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12/28/2011
10:53 AM
George Crump
George Crump
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Will RAID Die In 2012?

The time it takes to rebuild a RAID-protected volume makes it unwieldy with today's high-capacity drives.

RAID has become a staple of the modern day storage system, but as the number and capacity of drives in a storage system continue to increase, questions have risen about the viability of RAID. At issue is the amount of time it takes for a RAID-protected volume to rebuild itself after a drive failure. While in 2011 we saw many predictions of RAID's demise, it continues to be the protection algorithm of choice for most storage systems. Will 2012 be any different?

In Storage Switzerland's recent article What is RAID? we explain that RAID is a protection scheme that allows for volumes to have a drive failure and still be able to provide access to the data on that volume. The problem is that with today's drive technology the speed at which drives can be rebuilt is now measured in double-digit hours if not days. During this time performance can degrade and there is the risk of additional drive failure. If an additional drive fails beyond the RAID algorithms' allowance, then there is a complete data loss and recovery from backup software must begin.

There is also the reality that drives are more likely to fail as the capacity per drive increases. As drive capacity increases, so does the bit error rate (BER), which is essentially how much data can be read from a drive before you experience an unrecoverable read error. The BER ratio has stayed relatively the same while drive capacities have skyrocketed. A 2-TB drive is significantly more likely to encounter an error than a 1-TB drive when reading an entire drive, which is what happens during a RAID rebuild.

Given this combination of factors, it is likely that many large storage systems will be in a constant state of rebuild. Clearly the industry is dealing with this reality. We didn't abandon RAID 5 or RAID 6 last year. The most common "solution" has been to just live with the problem. Storage vendors can do this by making sure that there is enough storage controller processing power to provide adequate system performance while the rebuild is occurring. It would not surprise me to see some vendors allocate special standby processors to help with the rebuild process.

Another solution for RAID may be to use flash-based memory for all mission-critical data. While flash modules can fail just like hard drives, the performance of flash makes the rebuild process significantly faster. A rebuild of a flash volume protected by RAID is typically less than 15 minutes in our testing.

Eventually, though, we may just throw RAID out all together and go with an erasure coding algorithm or even more of a mirroring and replication strategy. After all, capacity is now inexpensive, and having a storage system that can automatically maintain x number of copies of data may be the simplest and most practical approach for data that is going to remain on a hard disk. This also gives you greater granularity by being able to set different levels of redundancy for different types or ages of data.

My expectation is that we will see a shift toward flash storage for mission-critical active data where RAID rebuilds will be less time-consuming and space efficiency is more important due to cost. Then we can use more of a replication, redundant copy strategy for older data stored on hard disk.

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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.

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Guest,
User Rank: Apprentice
1/6/2012 | 4:37:22 AM
re: Will RAID Die In 2012?
Nah, disk is dirt cheap. There were companies like Xiotech that tried to sell storage systems which would repair disks in place instead of just replacing them, but the price of disk and the size of disks came down so fast that people decided they would rather just replace them altogether than try to repair a couple of hundred dollar drive.

Check out XIV for controllers that use drives to their potential. The XIV controllers have an awesome algorithm that slices data into 1 MB chunks and spreads the data across every disk in the array (no more RAID planning). The controllers are attached to each disk module (not the standard dual controller bottleneck) so they work in tandem on IO requests, massive parallel processing, which allows disks to be rebuilt in about 30 minutes.
Guest
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Guest,
User Rank: Apprentice
1/6/2012 | 4:30:19 AM
re: Will RAID Die In 2012?
Definitely, disk is wicked cheap and RAID is used by everyone down to people in their dorm rooms making video productions. Flash is expensive. I think people will keep on keeping on with disk, maybe a little flash for hot objects, but move to an XIV or XIV-like architecture where the controller automatically slices the data into 1 MB chunks and spreads it across every disk in the array.
UberGoober
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UberGoober,
User Rank: Strategist
1/4/2012 | 7:42:49 PM
re: Will RAID Die In 2012?
"RAID is now mainstream, but with drive prices still being rather high it is not an option for most." Huh?

RAID was mainstream in the late '90s, and anyone who puts in a business server without RAID or equivalent today, even in a very small business, should turn in their (probably paper) credentials. Virtually every server and even most workstations include at least hardware mirroring, and the price of the extra drive(s) is a tiny fraction of the system and implementation cost.
YMOM100
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YMOM100,
User Rank: Apprentice
1/4/2012 | 12:44:02 PM
re: Will RAID Die In 2012?
RAID is now mainstream, but with drive prices still being rather high it is not an option for most. There is more value in a solid backup solution, which one needs with or without RAID.
What we really need is tremendously better quality drives. The prices remained high and the quality went down. At the same time competition went away with the numerous mergers. We see the results of that now, companies like Seagate now have one year warranties for most of their drives, mainly because that fits the live expectancy of their shoddy workmanship. It used to be that three and five year warranties were a competitive advantage, but since the market is already divvied up there is no jockeying for position.
Would be nice if SSD became a real alternative, but at three to four times the price of hard drives and much smaller capacities it is still a niche product.

As far as rebuilding RAIDs, maybe we just need faster controllers that fully use the drives' potentials?
Bprince
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Bprince,
User Rank: Apprentice
12/31/2011 | 3:00:57 PM
re: Will RAID Die In 2012?
More on the future of RAID:
http://searchstorage.techtarge...
Brian Prince, InformationWeek/Dark Reading, Comment Moderator
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Guest,
User Rank: Apprentice
12/29/2011 | 12:50:16 AM
re: Will RAID Die In 2012?
Yes, I think it will die. When IBM brought grid (or virtualized, if you like) storage to the mainstream market with XIV and demonstrated 30 minutes 2 TB disk rebuilds (in addition to not having to deal with RAID striping), everyone went in the same direction.
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