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RAID recomendations Expand / Collapse
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Posted Wednesday, January 11, 2012 4:55 PM


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Kenneth.Fisher (1/11/2012)
I appreciate ya'lls help with this. RAID has always been a difficult subject for me but I think I'm finally getting it down.

Just as an aside, we have the interesting problem of not always knowing where are drives are comming from. In other words, the D drive and the E drive may actually both be on the same RAID array, but no one told us, its just the way it was allocated out.

Are you planning to use local disks or SAN presented storage?


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Post #1234471
Posted Wednesday, January 11, 2012 5:03 PM


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I really don't like the questions about "best" practices for storage from MS. There is seldom enough information presented to properly answer those questions.

Sure, RAID10 offers better protection. RAID5 is cheaper. In discussions with EMC consultants as well as SQLIO sims you can get the same performance from both. If RAID5 is cheaper, you can add more disks and have more space in theory.

Case in point - at one client we had double the performance from RAID5 than the RAID10 (write and read were both better in SQLIO). Client could not afford to have RAID10 everywhere nor was there enough drive bays to compensate in favor of the RAID10.

If I had to use spinning disk then I would go RAID10 where possible. If I had the money I would use FusionIO not worry about the performance of the chosen array ;).




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Post #1234475
Posted Wednesday, January 11, 2012 5:10 PM


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The big advantage of Raid 10 is you can lose up to half the disks as long as no mirrored pair fail and the array will still operate, albeit with reduced performance.

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Post #1234478
Posted Wednesday, January 11, 2012 5:41 PM


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Perry Whittle (1/11/2012)
The big advantage of Raid 10 is you can lose up to half the disks as long as no mirrored pair fail and the array will still operate, albeit with reduced performance.


Biggest part of the reason I would go with RAID10 if possible - protection.




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Post #1234489
Posted Wednesday, January 11, 2012 6:24 PM


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Raid 5 has performed great for me in many applications. Many apps where we weren't pushing the envelope on IOPS, and we had much of the needed data in RAM.

The issue with R5 is that you need a spare handy when one fails because the degradation of performance, and risk, go up dramatically.







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Post #1234500
Posted Thursday, January 12, 2012 12:16 AM


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@SQLRNNR exactly, although if you were to lose half the drives performance would suck in a big way. Your data is still intact though.


@Steve Jones that is, unfortunately a disadvantage of the RAID5. Array rebuild times for R5 and R10 are also a consideration, with lower rebuild times R10 is often the favourite.


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Posted Thursday, January 12, 2012 8:25 AM


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Perry Whittle (1/12/2012)

@Steve Jones that is, unfortunately a disadvantage of the RAID5. Array rebuild times for R5 and R10 are also a consideration, with lower rebuild times R10 is often the favourite.


That's why you need a spare in the rack.

And if you do that, why not go with R10 then and slightly bigger drives? I've gambled on R5 in the past, but with today's capacities of drives, not sure I would anymore.

Side note: we started with R5 here in 2001, but when we purchased larger servers in 2005, we just went with multiple R1 arrays for protection since we were putting a spare drive in a 6 slot server, we just did 3 R1 arrays.







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