'Drives and Storage' Category Archive

Posted on Mar 25th, 2007

Data loss is an expensive reality. It’s a hard fact that it happens more often then users like to admit. A recent study by the accounting firm McGladrey and Pullen estimates that one out of every 500 data centers will experience a severe computer disaster this year. As a result, almost half of those companies will go out of business. At the very least, a data loss disaster can mean lost income and missed business opportunities.

The other side of data loss is the psychological and emotional turmoil it can cause to IT managers and business owners. Despair, panic, and the knowledge that the whole organization might be at risk are involved. In a sense, that’s only fair, since human error is one of the two largest contributing factors in data loss. Together with mechanical failure, it accounts for almost 75 per cent of all incidents. (Software corruption, computer viruses and physical disasters such as fire and water damage make up the rest.)

Disk drives today are typically reliable. Human beings, it turns out, are not. A Strategic Research Corp. study done in 2000 found that approximately 15 per cent of all unplanned downtime occurred due to human error. A significant proportion of that happened because users failed to implement adequate backup procedures, either having trouble with their backups, or having no backup at all.

How does it happen that skilled, high-level users put their systems - and their businesses - at such risk?

In many cases, the problem starts long before the precipitating system error is made, that is, when users place their faith in out-of-box solutions that may not, in fact, fit their organization’s needs. Instead of assessing their business and technology requirements, then going to an appropriate engineered solution, even experienced IT professionals at large corporations will often simply buy what they’re sold. In this case, faith in technology can be an vice instead of a virtue.

But human intervention itself can sometimes be the straw that breaks the technology’s back. When the office of a Venezuelan civil engineering firm was devastated by floods, its owners sent 17 soaked, mud-coated disks from three RAID arrays to us in plastic bags. A tough enough salvage job was made even more complex by the fact that someone had frozen the drives before shipping them. As the disks thawed, yet more damage was done. (After eight weeks of painstaking directory-by-directory recovery, all the data from the remaining fifteen disks was retrieved.)

Sometimes, the underlying cause of a data loss event is simply shoddy housekeeping. The more arduous the required backup routine, the less likely it will be done on a regular basis. A state ambulance monitoring system suffered a serious disk failure, only to discover that its automated backup hadn’t run for fourteen months. A tape had jammed in the drive, but no-one had noticed.

When disaster strikes, the normal human reaction is panic. Because the loss of data signifies critical consequences, even the most competent IT staff can jump to conclusions, and take inappropriate action. A blank screen at a critical time can lead to a series of naive decisions, each one compounding the preceding error. Wrong buttons get pushed, and the disaster only gets worse. Sometimes the pressure to correct the system failure speedily can result in an attempt to reconfigure an entire RAID array. IT specialists are typically not equipped to deal with crisis modes or data recovery techniques. Just as a good physician is trained to prolong life, the skilled IT specialist is trained to keep the system running. When a patient dies, the physician turns to others, such as nurses or counselors to manage the situation. When significant data loss occurs, the IT specialist turns to the data recovery professional.

Data recovery specialists are innovative problem solvers. Often, the application of basic common sense, when no-one else is in any condition to apply it, is the beginning of the journey towards data recovery. The data recovery specialist draws on a wealth of experience, married to a "never say die" attitude, and a comprehensive tool kit of problem-solving procedures. Successful recovery outcomes hinge on a combination of innovative logistics, applied problem-solving, and "technology triage," the process of stabilizing an affected system quickly, analyzing and treating its wounds, and preparing it for surgery. The triage process sets priorities, such as targeting which files are needed first or which are absolutely vital to the functioning of the business, and establishes whether files might be recovered in less structured formats (such as text-only), which may be desirable when time is crucial.

The art and science of professional data recovery can spell the difference between a business’ success or its failure. Before that level of intervention is required, though, users can take steps to ensure that the probability of a data loss disaster is minimized.

Basic to any business technology plan is a regular fire-drill procedure. Back-up routines may be in place, staff may assigned to specific roles, hardware and software may be configured - but, if the user isn’t completely sure that everything works the way it should, a data loss event is inevitable. Having adequate, tested, and current backups in place is critical. A hardware breakdown should not be compounded by human error - if the malfunctioning drive is critical, the task of dealing with it should go to a data recovery professional.

Just as data loss disasters are rooted in a combination of mechanical failure and human error, so, too, the data recovery solution lies in a creative marriage of the technological and the human. The underlying philosophy of successful data recovery is that technology is something to be used by human beings, not something that uses us.

Name: Darryl Peddle
C
ompany: CBL Technologies, Canada
Author description: Darryl Peddle is an Internet Marketing Specialist with CBL Technologies, one of the largest data recovery specialists in the world.
Website: http://www.cbltech.com

Posted on Mar 14th, 2007

Hard Drives: ATA versus SATA

The performance of computer systems has been steadily increasing as faster processors, memory, and video cards are continuously being developed. The one key component that is often neglected when looking at improving the performance of a computer system is the hard drive. Hard drive manufacturers have been constantly evolving the basic hard drive used in modern computer systems for the last 25 years, and the last few years have seen some exciting developments from faster spindle speeds, larger caches, better reliability, and increased data transmission speeds.

The drive type used most in consumer grade computers is the hearty ATA type drive (commonly called an IDE drive). The ATA standard dates back to 1986 and is based on a 16-bit parallel interface has undergone many evolutions since its introduction to increase the speed and size of the drives that it can support. The latest standard is ATA-7 (first introduced in 2001 by the T13 Technical Committee (the group responsible for the ATA standard)) which supports data transfer rates up to 133MB/sec. This is expected to be the last update for the parallel ATA standard.

As long ago as 2000 it was seen that the parallel ATA standard was maxing out its limitations as to what it could handle. With data rates hitting the 133MB/sec mark on a parallel cable, you are inviting all sorts of problems because of signal timing, EMI (electromagnetic interference) and other data integrity issues; thus industry leaders got together and came up with a new standard known as Serial ATA (SATA). SATA has only been around a few years, but is destined to become “the standard” due to several benefits to be addressed in this Tech Tip.

The two technologies that we will be looking at are: ATA (Advanced Technology Attachment) – a 16-bit parallel interface used for controlling computer drives. Introduced in 1986, it has undergone many evolutions in the last 18+ years, with the latest version being called ATA-7. Wherever an item is referred to as being an ATA device, it is commonly a Parallel ATA device. ATA devices are also commonly called IDE, EIDE, Ultra-ATA, Ultra-DMA, ATAPI, PATA, etc. (each of these acronyms actually do refer to very specific items, but are commonly interchanged) SATA (Serial Advanced Technology Attachment) – a 1-bit serial evolution of the Parallel ATA physical storage interface.

Basic Features & Connections

SATA drives are easy to distinguish from their ATA cousins by the different data and power connections found on the back of the drives. A side-by-side comparison of the two interfaces can be seen in this PDF from Maxtor, and the following covers many of the differences…

Standard ATA drives, such as this 200GB Western Digital model, have somewhat bulky, two inch wide ribbon cable with 40-pin data connections and receive the 5V necessary to power them from the familiar 4-pin connection. The basic data cables for these drives have looked the same for years. A change was made with the introduction of the ATA-5 standard to better improve the signal quality by making an 80 wire cable used on the 40-pin connector (these are commonly called 40-pin/80-wire cables). To improve airflow within the computer system some manufacturers resorted to literally folding over the ribbon cable and taping it into that position. Another recent physical change also came with the advent of rounded cables. The performance of the rounded cables is equal to that of the flat ribbon, but many prefer the improved system air flow afforded, ease of wire management, and cooler appearance that come with them.

SATA drives, such as this 120GB Western Digital model, have a half inch wide, 7 “blade and beam” data connection, which results in a much thinner and easier to manage data cable. These cables take the convenience of the ATA rounded cables to the next level by being even narrower, more flexible and capable of being longer without fear of data loss. SATA cables have a maximum length of 1 meter (39.37 inches), which is much greater than the recommended 18 inch cable for ATA drives. The reduced footprint of SATA data connections frees up space on motherboards, potentially allowing for more convenient layouts and room for more onboard features!

A 15-pin power connection delivers the 250mV of necessary power to SATA drives. 15-pins for a SATA device sounds like it would require a much larger power cable than a 4-pin ATA device, but in reality the two power connectors are just about the same height. For the time being, many SATA drives are also coming with a legacy 4-pin power connector for convenience.

Many modern motherboards, such as this Chaintech motherboard, come with SATA drive connections onboard (many also including the ATA connectors as well for legacy drive compatibility), and new power supplies, such as this Ultra X-Connect, generally feature a few of the necessary 15-pin power connections, making it easy to use these drives on new systems. Older systems can easily be upgraded to support SATA drives by use of adapters, such as this PCI slot SATA controller and this 4-pin to 15-pin SATA power adapter.

Optical drives are also becoming more readily available with SATA connections. Drives such as the Plextor PX-712SA take advantage of the new interface, although the performance will not be any greater than a comparable optical drive with an ATA connection.

Performance

In addition to being more convenient to install and drawing less power, SATA drives have performance benefits that really set them apart from ATA drives.

The most interesting performance feature of SATA is the maximum bandwidth possible. As we have noted, the evolution of ATA drives has seen the data transfer rate reach its maximum at 133 MB/second, where the current SATA standard provides data transfers of up to 150 MB/second. The overall performance increase of SATA over ATA can currently be expected to be up to 5% (according to Seagate), but improvements in SATA technology will surely improve on that.

The future of SATA holds great things for those wanting even more speed, as drives with 300 MB/second transfer rates (SATA II) will be readily available in 2005, and by 2008 speeds of up to 600 MB/second can be expected. Those speeds are incredible, and are hard to imagine at this point.

Another performance benefit found on SATA drives is their built-in hot-swap capabilities. SATA drives can be brought on and offline without shutting down the computer system, providing a serious benefit to those who can’t afford downtime, or who want to move drives in and out of operation quickly. The higher number of wires in the power connection is partially explained by this, as six of the fifteen wires are dedicated to allowing the hot-swap feature.

Price

Comparing ATA drives to SATA drives can be tricky given all of the variables, but in general it is the case that SATA drives will still cost just a bit more than a comparable ATA drive. The gap is closing rapidly though, and as SATA drives gain in popularity and availability a distinct shift in prices can be expected. Considering the benefits of SATA over ATA, the potential difference of a few dollars can easily be justified when considering an upgrade. Computer Geeks currently has a limited selection of SATA drives, but several technical sites, such as The Tech Zone and The Tech Lounge, offer real time price guides to see how comparable drives stack up.

Final Words

The current SATA standard provides significant benefits over ATA in terms of convenience, power consumption and, most importantly, performance. The main thing ATA has going for it right now is history, as it has been the standard for so long that it will not likely disappear any time soon. The future of SATA will be even more interesting as speed increases will help hard drive development keep pace with other key system components.

Jason Kohrs Computer Geeks tech tips and computer advice

Posted on Mar 11th, 2007

Thinking about a mini DVD camcorder? You’re not alone, it’s a rapidly growing sector of the camcorder market, with Hitachi, Sony and Panasonic all making more than one mini dvd camcorder.

These camcorders differ from regular digital video cameras in one important way - they record video onto mini DVD discs, rather than DV tape. This has a number of advantages. DVD discs are more robust than tape and won’t get chewed up in the camera. Although this is thankfully a rare occurance, it scares me every time I here a strange noise coming from my camcorder, so it’s with bearing in mind.

The second advantage is that DVD discs are random access, compared to tape on which everything is recorded sequentially. This means that there’s no need to rewind and fast forward to find the clip you’re after, just select it from the menu. Some cameras even allow you to perform basic editing functions on-camera. An additional side-benefit is that a mini DVD camcorder doesn’t have tape heads to get worn or dirty as happens in regular mini DVD cameras.

And thirdly, you can easily watch your home movies by removing the DVD from the camera and playing it in practically any DVD player.

However, there are negative factors to. The most siginificant one is that video is encoded as MPEG-2 on a mini DVD camcorder, as opposed to DV format. This means that it needs specialist software to edit - you can’t just use your regular video editing program (unless it specifically supports MPEG-2). And if a Mac user you’re out of luck, as there are no MPEG-2 editing applications for the Mac.

Also, mini DVD camcorders tend to cost more than similarly specified mini DV cameras. And the media is also more expensive. However, if you don’t intend editing your movies and don’t mind the extra cost, a mini dvd camcorder does offer extraordinary convenience.

Kenny Hemphill is the editor and publisher of The HDTV Tuner, a site which aims to cut through the confusion surrounding HDTV and provide surfers with up to date, accurate and easy to read information on HDTV.

Posted on Mar 10th, 2007

Picking your way through the ton of information available on recordable DVD formats can be a nightmare. To help you out, we’ve done our best to distill it into this summary.

There are five recordable versions of DVD; DVD-R for General, DVD-R for Authoring, DVD-RAM, DVD-RW, and DVD+RW. None of the formats is fully compatible with the other although there are drives which will read, and in some cases write to more than one format.

DVD-R for General and DVD-R for Authoring are essentially DVD versions of CD-R. And DVD-RW is a DVD version of CD-RW. All three formats can be read in standard DVD-ROM drives and in most DVD video players. The difference between DVD-R for General and DVD-R for Authoring is that DVD-R for General is a format intended for widespread consumer use and doeasn’t support ‘professional’ features such as piracy protection or duplication in mass duplicators. The Pioneer DVD-RW drive which is the most popular PC device for writing to DVD uses the DVD for General format. And as as the case with CD, DVD-RW is essentially the same as DVD-R except that it can be erased and written to again and again.

DVD-RAM is slightly different as it is a sector based disc which mounts on the desktop of a PC when inserted into a drive. Files can then be copied to it in the same way as any other mounted media. Some single-sided DVD-RAM discs can be removed from their caddy and inserted in a DVD-ROM drive which will then be able to read the content of the disc.

There are DVD video recorders which use the DVD-RAM format. This enables themn to pull off clever tricks like timeshifting – where you can watch the beginning of a programme you have recorded while you are still recording the end on the same disc.

DVD+RW is the newest format and not supported by the DVD Forum, the body which sets the standards for DVD. However, it is supported by some of the biggest electronics and computer manufacturers, and is therefore likely to stick around.

It is also the format used by Philips in its DVD video recorders. Despite not being authorised by the DVD Forum, DVD+RW is claimed by its supporterd to be compatible with more DVD video players than DVD-R and DVD+RW writers are found in PCs from quite a few manufacturers.

In early 2006, things are set to get even more complicated with the introduction of two new formats, HD-DVD and Blu-ray, but that’s a whole other story…

Kenny Hemphill is the editor and publisher of The HDTV Tuner, a site which aims to cut through the confusion surrounding HDTV and provide surfers with up to date, accurate and easy to read information on HDTV.

Posted on Mar 8th, 2007

The internet is full of technical articles, many of which are way too complicated for the average computer user who just wants to solve a simple problem. If you pay close attention, the internet is also a place where the "gurus" spend a lot of time yelling for help in discussion boards and forums. So don’t feel bad, nobody has all the answers.

So you want to dual boot Windows and Linux on the same computer—it is really quite easy. I only have enough room here to tell you the most common way to do this on a single hard drive or using multiple hard drives. Obviously then, there are many ways to get the job done, but there are some critical things you should know. Let’s start with some critical information.

Windows and Linux: Same Hard Drive The windows operating system MUST occupy the master boot record (MBR). Linux, on the other hand does not have to. In this scenario, you must install windows first! After Windows has been successfully installed, then you can install Linux. This is critical! The Linux "boot loader" is called GRUB. When you install Linux—MAKE SURE YOU DO NOT INSTALL THE LINUX BOOT LOADER TO THE MBR.

Configure the Windows Boot Loader: A Two Step Process It is also possible to use GRUB to dual boot Windows and Linux on the same drive but this is a bit more complex—the Windows boot loader will get the job done. In the following commands, you will create a copy of the Linux boot sector and then save it in a file in the top level directory under Windows (C:).

Step 1: Linux From the shell in your Linux installation (boot from your installation disks): Execute the following shell command, replacing /dev/hda3 with the location of your Linux boot partition.

shell# dd if=/dev/hda3 of=/bootsect.lnx bs=512 count=1

Copy the new file—bootsect.lnx—to a floppy disk and reboot to Windows.

Step 2: Windows Copy bootsect.lnx to C: in Windows. Then execute the following command at the DOS prompt.

C:> attrib -H -R -S boot.ini

Edit boot.ini so that the first two lines are:

[boot loader] timeout=30

After the last line, add:

c:bootsect.lnx="Start Linux"

That’s it, you are done! Reboot your machine and you will see a menu allowing you to select either Windows or Linux. Congratulations.

Windows and Linux: Two Hard Drives This is also quite easy. In this case, you will boot to the Linux drive. We will add Windows to the Linux boot loader (i.e., GRUB). GRUB is my favorite boot loader.

Edit the /boot/grub/grub.conf file. One of the very first lines should contain:

timeout=30

After the last line add:

title Start Windows map (hd1) (hd0) map (hd0) (hd1) rootnoverify (hd1,0) makeactive chainloader +1

Reboot your machine to the Linux drive and you will see a menu allowing you to select between Linux or Windows. Nice work!

This article is obviously short and does not include any explanations of how these commands work. There are variations on what I have shown here depending on your hardware setup, but I believe that these are the most common and should get the job done nicely. I would be happy to direct you to additional resources if this does not work for you.

Copyright 2005 Majella.us

David Picella is a Family Nurse Practitioner and PhD Student at UW Milwaukee. You can find additional technichal resources for this article in the technology section at: http://www.majella.us

Posted on Mar 8th, 2007

IMO, these sd work ‘like a VCR’ as far as recording and playback. There are models w/ harddrives, VHS players, etc. built in, but to me that’s overboard.

Bells and Whistles

The VHS option is not bad, but you most likely already have one you can plug into the inputs of the DVD recorder.

I have a DVD recorder for archiving TiVo shows as opposed to accessing my TiVo from my PC. This is nice because it means I can also archive VHS tapes, camcorder tapes, etc. w/no extra work.

I do have a TV card in my PC so I can do this, but using the DVD recorder is easier.

My motto is: buy what you WILL use and not what you CAN use.

I’ve bought lots of things that CAN do a lot, but in reality I don’t use all the extra features. Not in all cases, but in this case, I say pass on the bells and whistles.

Again, there are models w/ all types of features, but if you buy one that is a DVR, DVD recorder, VCR, TV tuner all in one and one part breaks, it’s all broke.

Realize Something About Technology

Remember - this is new technology and will only get better and cheaper. If you buy the top of the line today, it’s going to be out of date and/or cheap tomorrow. Test the waters w/ a ‘good’ model and upgrade when the time is right.

Editing Your Recordings

Chances are - you won’t. It’s a pain for the most part and usually requires DVD-RAM or DVD-RW discs to do it and they’re more expensive. If you have a lot of free time for this, you’re a rare person.

I was looking for this type of solution in getting ready for having a baby and I knew I wasn’t going to be sifting through and editing hours of video.

If you’re really interested in editing, look in to PC options. Pinnacle, ArcSoft, Adobe, etc. - they have good solutions for that.

DVD+R, DVD-R, DVD-RAM, DVD-RW

DVD+R and DVD-R are like VHS and Beta: they’re both ok right now, but eventually we’ll probably land on one or the other. It seems to be leaning towards DVD-R which tend to be less expensive also.

Many recorders and players do both, but cost more. I say save some money, pick one (probably DVD-R) and move on. If you pick the wrong one, chances are in a couple years you’ll be buying a new one anyway. Moreover, you’ll probably be able to get a cheap one w/ a built in converter or two trays to duplicate one to the other.

DVD-RAM and DVD-RW are the rewritable types. They’re more expensive and for my purposes aren’t worth worrying about.

My Recommendation

I got the Panasonic DMR-E55K:

It records to DVD-R like a VCR. I don’t use it to record live TV so I don’t use VCR+, but it has it. Also, it has TimeSlip which lets you watch something while it’s recording (start recording "24" at 8pm and start watching it from the begining at 8:20 to speed thru commercials like a TiVo). Again, I don’t use this, but it has it.

Plain and simple, it records my TiVo, camcorder, digital camera (RCA cable output), VCR, etc. to DVD - that’s what I want it to do and that’s what it does. It’s easy, creates a good menu w/ thumbnails and my chosen titles, it’s a name brand w/ good reviews and was fairly cheap (there was a rebate at the time).

Also, it plays CDs and mp3 CDs w/ a good interface so not only does it replace a CD player, but since you can put so many songs on one CD, it replaces a CD changer.

An interesting trick: If you have a digital camera w/ RCA cable output, you can hook it directly into the dvd recorder and create a quick slide-show dvd. Many cameras even have a slide show function built in! You can use the sound from a music channel, CD, etc.

Summary

If you’re going gung-ho into all the nitty gritty about DVD recorders, you’re either just starting here or haven’t bothered to read this far. If you’re looking for a good, relatively cheap solution to digitize your tapes, archive TiVo, etc., I recommend the Panasonic DMR-E55K.

Bear Cahill is a software engineer in the Dallas, TX area and runs a few websites: The Armchair Geek (thearmchairgeek.com), Webpage Hosting Info (webpagehostinginfo.com), Go To College Online (gotocollegeonline.com) and The Video Exchange Community (videoexchange.org)

Publish freely if this resource box is included and links maintained as links.

Posted on Mar 5th, 2007

A couple of the recent Tech Tips from www.geeks.com have made mention of RAID, but the level of detail required in those tips didn’t shed much light on what RAID actually is. The number of e-mail responses and comments in the Readers Digress section was convincing enough that an introduction to the basics of RAID would be an appropriate Tech Tip, so here it is.

Introduction

The word RAID sounds like it might describe something Marines conduct in Fallujah, or a can of what all roaches fear, but it is simply an acronym that stands for Redundant Array of Independent (or Inexpensive) Disks. Depending on who you talk to, the letter “I” can stand for either independent or inexpensive, but in my opinion independent is more appropriate, and far less subjective.

RAID generally allows data to be written to multiple hard disk drives so that a failure of any one drive in the array does not result in the loss of any data, as well as increasing the system’s fault tolerance. I say RAID generally does this, as there are several RAID configurations that provide different approaches to redundancy, but some RAID configurations are not redundant at all. Fault tolerance refers to a system’s ability to continue operating when presented with a hardware (or software) failure, as should be experienced when a hard drive fails in one of the redundant configurations of RAID.

The Hardware

The basic hardware required to run RAID includes a set of matched hard drives and a RAID controller.

RAID can be run on any type of hard drive, including SCSI, SATA, and ATA. The number of hard drives required is dependent on the particular RAID configuration chosen, as described later. I mention the need for matched hard drives, and although this is not absolutely necessary, it is recommended. Most arrays will only be able to use the capacity of the smallest drive, so if a 250GB Hitachi drive is added to a RAID configuration with an 80GB Hitachi drive, that extra 170GB would probably go to waste (the only time that this doesn’t apply is in a RAID configuration called JBOD (Just a Bunch Of Disks); which really “isn’t a RAID configuration” but just a convenient thing that a RAID controller can do – see “Basic RAID Configurations” below for more information). In addition to matching capacities, it is highly recommended that drives match in terms of speed and transfer rate as the performance of the array would be restricted by the weakest drive used. One more area that should be considered while matching is the type of hard drive. RAID controllers are generally for either SCSI, SATA, or ATA exclusively, although some systems allow RAID arrays to be operated across controllers of different formats.

The RAID controller is where the data cables from the hard drives are connected, and conducts all of the processing of the data, like the typical drive connections found on a motherboard. RAID controllers are available as add on cards, such as this Silicon Image PCI ATA RAID controller, or integrated into motherboards, such as the SATA RAID controller found on the Asus K8V SE Deluxe (http://www.geeks.com/details.asp?invtid=K8VSE-DELUXE). Motherboards that include RAID controllers can be operated without the use of RAID, but the integration is a nice feature to have if RAID is a consideration. Even for systems without onboard RAID, the relatively low cost of add on cards makes this part of the upgrade relatively pain free.

Another piece of hardware that is not required, but may prove useful in a RAID array is a hot swappable drive bay. It allows a failed hard drive to be removed from a live system by simply unlocking the bay and sliding the drive cage out of the case. A new drive can then be slid in, locked into place, and the system won’t skip a beat. This is typically seen on SCSI RAID arrays, but some IDE RAIDS cards will also allow this (such as this product manufactured by Promise Technology: http://www.promise.com/product/product_detail_eng.asp?productId=92&familyId=7).

The Software

RAID can be run on any modern operating system provided that the appropriate drivers are available from the RAID controller’s manufacturer. A computer with the operating system and all of the software already installed on one drive can be easily be cloned to another single drive by using software like Norton Ghost. But it is not as easy when going to RAID, as a user who wants to have their existing system with a single bootable hard drive upgraded to RAID must start from the beginning. This implies that the operating system and all software needs to be re-installed from scratch, and all key data must be backed up to be restored on the new RAID array.

If a RAID array is desired in a system for use as storage, but not as the location for the operating system, things get much easier. The existing hard drive can remain intact, and the necessary configuration can be made to add the RAID array without starting from scratch.

Basic RAID Configurations

There are about a dozen different types of RAID that I know of, and I will describe five of the more typical configurations, and usually offered on RAID controller cards.

RAID 0 is one of the configurations that does not provide redundancy, making it arguably not a true RAID array. Using at least two disks, RAID 0 writes data to the two drives in an alternating fashion, referred to as striping. If you had 8 chunks of data, for example, chunk 1, 3, 5, and 7 would be written to the first drive, and chunk 2, 4, 6, and 8 would be written to the second drive, but all in sequential order. This process of splitting the data across drives allows for a theoretical performance boost of up to double the speed of a single hard drive, but real world results will generally not be nearly that good. Since all data is not written to each disk, the failure of any one drive in the array generally results in a complete loss of data. RAID 0 is good for people who need to access large files quickly, or just demand high performance across the board (i.e. gaming systems). The capacity of a RAID 0 array is equal to the sum of the individual drives. So, if two 160GB Seagate drives were in a RAID 0 array, the total capacity would be 320GB.

RAID 1 is one of the most basic arrays that provides redundancy. Using at least two hard drives, all data is written to both drives in a method referred to as mirroring. Each drive’s contents are identical to each other, so if one drive fails, the system could continue operating on the remaining good drive, making it an ideal choice for those who value their data. There is no performance increase as in RAID 0, and in fact there may be a slight decrease compared to a single drive system as the data is processed and written to both drives. The capacity of a RAID 1 array is equal to half the capacity of the sum of individual drives. Using those same two 160GB Seagate drives from above in RAID 1 would result in a total capacity of 160GB.

RAID 0+1, as the name may imply, is a combination of RAID 0 and RAID 1. You have the best of both worlds, the performance boost of RAID 0 and the redundancy of RAID 1. A minimum of four drives is required to implement RAID 0+1, where all data is written in both a mirrored and striped fashion to the four drives. Using the 8 chunks of data from the example above, the write pattern would be something like this… Chunks 1, 3, 5, and 7 would be written to drives one and three, and chunks 2, 4, 6, and 8 would be written to drives two and four, again in a sequential manner. If one drive should fail, the system and data are still intact. The capacity of a RAID 0+1 array is equal to half the total capacity of the individual drives. So, using four of the 160 GB Seagate drives results in a total capacity of 320GB when configured in RAID 0+1.

RAID 5 may be the most powerful RAID configuration for the typical user, with three (or five) disks required. Data is striped across all drives in the array, and in addition, parity information is striped as well. This parity information is basically a check on the data being written, so even though all data is not being written to all the drives in the array, the parity information can be used to reconstruct a lost drive in case of failure. Perhaps a bit difficult to describe, so let’s go back to the example of the 8 chunks of data now being written to 3 drives in a RAID 5 array. Chunks one and two would be written to drive one and two respectively, with a corresponding parity chunk being written to drive three. Chunks three and four would then be written to drives one and three respectively, with the corresponding parity chunk being written to drive two. Chunks five and six would be written to drives two and three, with the corresponding parity chunk being written to drive one. Chunks seven and eight take us back to the beginning with the data being written to drives one and two, and the parity chunk being written to drive three. It might not sound like it, but due to the parity information being written to the drive not containing that specific bits of information, there is full redundancy. The capacity of a RAID 5 array is equal to the sum of the capacities of all the drives used, minus one drive. So, using three of the 160GB Seagate drives, the total capacity is 320GB when configured in RAID 5.

JBOD is another non-redundant configuration, which does not really offer a true RAID array. JBOD stands for Just a Bunch Of Disks (or Drives), and that is basically all that it is. RAID controllers that support JBOD allow users to ignore the RAID functions available and simply attach drives as they would to a standard drive controller. No redundancy, no performance boost, just additional connections for adding more drives to a system. A smart thing that JBOD does is that it can treat the odd sized drives as if they are a single volume (thus a 10GB drive and a 30GB would be seen as a single 40GB drive), so it is good to use if you have a bunch of odd sized drives sitting around – but otherwise it is better to go with a RAID 0, 1 or 0+1 configuration to get the performance boost, redundancy or both.

Final Words

Implementing RAID may sound daunting to those unfamiliar with the concept, but with some of the more basic configurations it is not much more involved than setting up a computer to use a standard drive controller. But, the benefits of RAID over a single drive system far outweigh the extra consideration required during installation. Losing data once due to hard drive failure may be all that is required to convince anyone that RAID is right for them, but why wait until that happens.

Computer Geeks tech tips and computer advice

Posted on Mar 3rd, 2007

Finally - and yes possibly because of mp3 players and the continuing development of such - the cost of Solid State computer memory is dropping.

Camera memory cards or sticks as some people call them are very well priced and readily available, you can now get up to 2gb, and in some cases 4gb units depending on the brand and type of card you require, USB flash/pen drives can now be bought in up to 2gb and no doubt higher in the near future.

This is where it gets interesting, you can now buy solid state, hard drives of up to 4gb which work on the same NAND flash chip technology as used on the solid state MP3 players like the iPod Nano and Sandisc M200. This NAND flash memory is available in units that fit directly into your computers standard IDE ATA interface socket, saving you space with no cables to get in the way and other designs will slot along side or below your existing hard drives and wire into your IDE ATA slots with your standard cables.

Both of these units are designed to work in very demanding conditions as they have no moving parts like your existing hard drives, with advantages including a faster data access and transfer rate, a lower power consumption and no noise.

Main Features of these units:
- Fully Compatible With IDE Interface
- Complies with Standard ATA Interface
- No noise
- No Seek Error
- Very high Shock Resistance
- No Latency Delay
- Low Power Consumption
- Highest Product Quality and Fastest data access
- Error Correction and Wear Leveling
- Extended Product life (excess of 3-million hours of - operation)
- Industry Standard interfaces
- Plug-in adaptation without proprietary connections
- Densities from 16MB to 4GB+
- Factory OS Format: use Out-of-the-Box, just add applications/code
- Extended Temperature Range

These Solid state - NAND type - Hard drives are another part of our future - today. To learn more and checkout the specifications follow this link to Solid State Hard drives

© Copyright 2005, Charles West, all rights reserved.

Charles West sells Technology products (cameras, DVD’s, sound systems and of coarse MP3 players etc) for a retailer. Over the last couple of years he has developed http://www.4-your.com and http://www.mp3srock.com In the process he has learnt many aspects about ‘The Web’ and all its variables, come accross many products, some good some not so good. The good ones are worth telling people about, so have a read there is always something new.

Posted on Feb 24th, 2007

High definition DVD, also known as HD-DVD (which actually stands for High Density DVD), is one of two competing high definition storage format - the other being Blu-ray.

The need for a new, high capacity storage format, has been primarily brought about by the rapid rise in popularity of HDTV in Japan and the US. HDTV has much higher bandwidth than either NTSC or regular DVD discs, so in order to record programs from HD- DVD higher capacity discs, of at least 30GB, are required.

High definition video is also being used increasingly to make Hollywood movies as it offers comparable quality to film at much less cost. Therefore, the studios plan to release future movies on one or both high definition formats.

HD-DVD was developed by Toshiba and NEC and has the support of the DVD Forum, along with a number of Hollywood studios. Currently those studios which have announced support for HD-DVD are; Universal Studios, Paramount Studios, Warner Bros., and New Line Cinema. It has a capacity of 15GB for single-sided discs and 30Gb for double-sided. It doesn’t need a caddy or cartridge and the cover layer is the same thickness as current DVD discs, 0.6mm. The numerical aperture of the optical pick-up head is also the same as DVD, 0.65mm.

Because of its similarities to current DVD, high definition DVD is cheaper to manufacture than Blu-ray, because it doesn’t need big changes in the production line set-up. Both HD-DVD and Blu-ray have backward compatibility with existing DVDV discs. That is that current DVDs will play in HD-DVD player, although new high definition DVD won’t play in older DVD players.

High definition DVD currently supports a number of compression formats, including MPEG-2, VC1 (based on Microsoft’s Windows Media 9), and H.264 which is based on MPEG-4 and will be supported by the next version of Apple’s QuickTime software, which will be included with Mac OS X Tiger.

Kenny Hemphill is the editor and publisher of The HDTV Tuner - a guide to the kit, the technology and the programming on HDTV.

Posted on Feb 22nd, 2007

RAID is short for Redundant Array of Independent (or Inexpensive) Disks, a category of disk drives that employ two or more drives in combination for fault tolerance and performance. RAID disk drives are used frequently on servers and increasingly being employed on personal computers. Array is the operative word, which also dictates what the cure is going to be, when a RAID disk recovery situation arises.

RAID disk repair, as you may expect is quite a complicated process. But the good thing going for it is the chances for retrieving lost data is higher than with most other types of disks because the typical RAID architecture strategically distributes data randomly across the array. What this sort of architecture demands of recovery professionals is to specialize in the disk’s many different levels.

In a nutshell, these are all the levels that the RAID disk recovery team is up against. RAID 0, 1, 0+1; RAID 3, 4; RAID 5; RAID 10; Hardware RAID including: AMI, Compaq, Dell, Adaptec, IBM, etc.; and, Software RAID including Mac OS; Windows Servers including 2K, XP, NT; Linux, Solaris, Novell, etc.

Just some RAID systems that most RAID disk recovery specialists should all be familiar with are: Quantum Snap Server; Maxtor MaxAttach; Adaptec AAA131; Compaq; Dell Perc Systems; IBM; AMI; Mylex; and yes, many others!

The two most common implementations of the RAID architecture are Levels 4 and 5. Level 4 provides block stripping with a parity check. When a data disk fails, the parity data is used to create a replacement disk. Level 5 provides data stripping at the byte level and also stripe error correction information, which results in excellent performance and good fault tolerance. These two types are certainly the best friends of the RAID disk recovery expert as these are the easiest to restore when the situation arises.

Brad Triggs provides more information on Data Recovery at his website:
Data-Recovery-Central.com - RAID Data Recovery

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