RAID for Rookies
Sheltering from the RAID
Published: 6th February 2013 | Source: OC3D | Price: |
Background
As anyone with an interest in enthusiast PCs and hardware will know, acronyms are thrown around hardware circles with more hapless abandon than the viral "... I took an arrow to the knee" Skyrim quote. The poignant acronym for this article will be... RAID.
Before we begin, let me just say that you shouldn't be afraid of RAID because it is deemed 'enthusiast' - modern computer systems allow the most complex RAIDs to be setup (far too) easily. Instead, you should be afraid of how addictive the performance and utility of a solid RAID setup can be!
Historically, RAID was shorthand for 'redundant array of inexpensive disks', however, as our bank managers can attest to, storage media is far from inexpensive. If you were feeling particularly anal at the time, you could have probably attempted to sue a manufacturer for price misrepresentation!
On this basis, the term was revised to represent a 'redundant array of independent disks' - cleverly emphasising the combination of multiple, separate, hard-disks without placing an expectation for cost-saving on the part of the consumer.
RAID Overview
So, right about now you'll be wondering what a RAID actually is - physically and logically. Allow me to elaborate upon these.
Physically, as the revised acronym allows you to discern, it is many hard-disks operating, logically, in unison as a single storage device. These disks have commonly been assumed to be identical (i.e. same manufacturer and model) in order to firstly create the array, and for the array to main operable integrity. This is where raw evidence actually edges towards the 'disproven' camp.
There are two terms that are important at this point - heterogeneous and homogenous. The former, heterogeneous, refers to a RAID setup which would be created from multiple different hard-disk drives. The latter, homogenous, is a RAID setup that would consist of near-identical hard-disk drives.
Several years ago, during the construction of a new-build backup server, I tested the differences between the traditional 'same-disk' RAID and an adhoc RAID, composed of differing vendor hard-disks. The results were very close - marginal read/write improvements were gained from the same-disk RAID setup, but the difference was slight - in the order of 25MB/sec average read/write over the adhoc RAID.
The importance of this factor is impossible to quantify for an enthusiast. The spare drives you may have access to would inherit cost-saving that could, depending on your goals, far outweigh the marginal 25MB per second read/write decrease you would notice when compared with a pricey new homogenous RAID setup.
"I used to be a rookie until I took an arrow in the... disk-drive" (sorry)
Most Recent Comments
Welcome to the team, Matt.
However, as an ex-storage consultant, please permit me to point out a few niggles
Page 2 - Raid 5 : You mention "Instead of the traditional mirroring of stripes"... I believe this should read "striping of mirrors" as you aptly described in the Raid 1+0 section above. Remember that striping of mirrors offers greater redundancy than mirroring of stripes (raid 1+0 is better than 0+1).
Page 2 - Raid 6 : The parity is not mirrored, it should be (in any decent implementation) a completely separate parity generation - this offers extra protection against bad blocks that store Raid-5 parity data during rebuild operations.
Page 3 - Mirroring : This attribute offers substantial performance gains for read operations, but none for write operations.
Page 3 - Raid FAQ 1 : Performance improvements are in-line with hard drives, eg: Raid-0 across 2 SSDs will double the throughput in both read and write operations. While real-life improvements may barely be noticeable, the performance increase is real. Also TRIM is now supported in Raid-1, so I argue that wear-rates are not substantially increased over a single SSD. I do agree it rarely makes financial sense though
Raid FAQ 3 : It is very possible to partition your different size drives and then use software RAID across like-size partitions. Leaving you with free partitions you can use for data storage, with the proviso they have no redundancy. Eg: 2TB + 500gb - partition the 2TB into 1.5TB + .5TB, then RAID across the 500gb partition and the 500gb drive. You can subsequently use the 1.5TB partition as normal.
I fully approve of the work you've put in to this and it is overall very good
I am however anally retentive having done this for a living for a while so I hope you'll take my comments as "constructive criticism" rather than any kind of dig
Keep up the good work!
Spaceboy - i'm honestly impossible to offend, so don't worry about that. The article was aimed at beginners, so my intention was lay some basic phrases and general understanding in this article, and then 'polish it up' in future advanced articles.
I do bow to your knowledge on this subject though, I am but a Jack of All, Master of None, based on the comparison between our job roles!
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Originally Posted by ugiboy
Hi, very impressive & informative article, well done Matt, I look forward to the follow ups. If I have understood this correctly (which is doubtful) putting SSD's into Raid0 array has no performance benefits & speeds up degradation? I look forward to anyones opinions/thoughts. Cheers
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Yeah you have not got the grasp of it at all..... LOL
Q: Can I use Solid-state drives for a super-fast array?A: Yes and no... SATA3 and PCI-E SSDs are already ridiculously fast - RAIDing them will either present negligible performance improvement (for RAID0), or in the case of the mirroring and parity RAIDs, will greatly increase the wear rate of the SSDs, therefore reducing their lifespan. So it *is* possible, but it does not make financial sense in my honest opinion!
Tom, I have taken this from the FAQ section of the review. So can you explain what i have not grasped please. Cheers
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Originally Posted by ugiboy
Beginner RAID FAQs
Q: Can I use Solid-state drives for a super-fast array?A: Yes and no... SATA3 and PCI-E SSDs are already ridiculously fast - RAIDing them will either present negligible performance improvement (for RAID0), or in the case of the mirroring and parity RAIDs, will greatly increase the wear rate of the SSDs, therefore reducing their lifespan. So it *is* possible, but it does not make financial sense in my honest opinion! Tom, I have taken this from the FAQ section of the review. So can you explain what i have not grasped please. Cheers |
You said about raid 0- that does make them a shit load faster even with onboard raid or software raid. The statement about degradation with other arrays is correct though but no different to intensive use.
Ive got 2x 480GB Corsair Force 3 GT's in Orca in Raid0 - read and write on the arrany is over 1GB/s
http://www.anandtech.com/show/6477/t...therboards-too
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Originally Posted by Soda-88
RAID0 TRIM is supported by Intel's 6 and 7 series chipsets.
http://www.anandtech.com/show/6477/t...therboards-too |
I look forward yo reading more in the futureAnd welcome
It may support TRIM, but that is simply on separate SSDs, not on RAID perhaps?
On the official page for your mobo, it mentions RAID0, not RAID5 - speed is obtainable, but the lifespan and speed of the drive/s may be compromised without TRIM/hardware controlled garbage collection.
Microsoft advise that you can verify TRIM being active (not just able to be supported) through these steps:
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1. Start Menu > Run > "fsutil behavior query DisableDeleteNotify" If the result is '0' TRIM is available (not necessarily active) 2. Install and run Intel's SSD Toolbox program (http://downloadcenter.intel.com/Deta...&DwnldID=18455) 3. Select your SSD and click "View Drive Information" (it doesn't matter whether it's an Intel SSD or some other brand) 4. In the "Word" column, scroll down to '169'; the description should be, "Data Set Management Support" 5. A couple of lines down from that, look for "Bit 0 - Data Set Management Supported" 6.If the Hex Value associated with that reads '1', the drive is ready to receive TRIM commands from the OS That, along with the 'fsutil' command, should be sufficient to assume that TRIM is operating properly. |
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Originally Posted by ugiboy
Hi, thank you for taking the time to reply and for the instructions. I have Intel's SSD Toolbox V3.1.2 and when i click the "View Drive Information" nothing happens? I will download it again to see if it works and hopefully follow your instructions. Thanks again Glen Hi, I have entered what you said in "command prompt" and it is telling me DisableDeleteNotify = 0. If i understand you correctly that means that "Trim" is enabled? Thanks Glen
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