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What would be the best RAID configuration for this hardware? Expand / Collapse
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Posted Wednesday, November 14, 2012 10:40 AM


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I spoke with our Tech Services guy and he said there'd be no issue using a RAID5 with 12 disks, it would give us ample space and yield 11 available spindles. This should provide quick performance with a 9-1 read/write ratio.

Unfortunately I'm not much of a hardware guy But I suppose I'll just need to test it out to see


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Post #1384767
Posted Thursday, November 15, 2012 8:09 AM


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I think with so few spindles carving them up into smaller sets just sets yourself up for one or more of those smaller groups to be a bottleneck. I would lump them all together, and chose RAID 5 or 10 based on a) needed formatted disk size and b) IO testing metrics verifying I could get the read/write performance mix I required.

Best,

Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru at GMail
Post #1385183
Posted Thursday, November 15, 2012 11:55 AM


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TheSQLGuru (11/15/2012)
I think with so few spindles carving them up into smaller sets just sets yourself up for one or more of those smaller groups to be a bottleneck. I would lump them all together, and chose RAID 5 or 10 based on a) needed formatted disk size and b) IO testing metrics verifying I could get the read/write performance mix I required.

i agree, hence my previous comment to test various array types and number of disks


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Post #1385294
Posted Thursday, November 15, 2012 12:30 PM


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Yes, this is the option I am going with first (lumping all disks into a single RAID 5 array). I believe keeping one as a hot spare leaves me with 10 working spindles - with any luck I'll be able to test with SQLIO and SQLIOsim in the next couple days.

Thanks for everyone's help!


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Post #1385308
Posted Thursday, November 15, 2012 2:03 PM


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test a couple of smaller arrays too as well as RAID5 vs RAID10

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Post #1385361
Posted Thursday, November 15, 2012 3:32 PM


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Running some tests using IOMeter (preferred the GUI to this one over SQLIOsim) and using some of the predefined options here's the results:

ON a 12-disk, RAID 5, 1 hot-swappable spare, this uses 1 worker, 40,000,000 sectors (20GB file)

MAX IOPS - uses 4KB transfer request size, 100% reads, 100% sequential dist.:
TOT IO/sec: 121,432
Total MB/sec: 479
Average IO Response Time: 0.13
MAX IO Response 1.85
CPU: 26.5

MAX IOPS - uses 4KB transfer request size, 100% reads, 100% sequential dist.:
TOT IO/sec: 58,294
Total MB/sec: 227
Average IO Response Time: 0.27
MAX IO Response 86.9
CPU: 12.1

MAXIOPS with 90% read, 10% write ratio - uses 4KB transfer request size, 90% reads, 10% sequential dist.:
TOT IO/sec: 7000
Total MB/sec: 90
Average IO Response Time: 2.28
MAX IO Response 37.2
CPU: 27.6

I don't really know if this is good or not, when i ran it against on of the other RAID 10 arrays the numbers were much slower...so i assume this is good - Is this considered ok?


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Post #1385380
Posted Thursday, November 15, 2012 3:42 PM


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MyDoggieJessie (11/15/2012)
Running some tests using IOMeter (preferred the GUI to this one over SQLIOsim)

Errm, for benchmarking your I\O capacity (which is what you're doing here) you need to be using SQLIO or IOMeter.
SQLIOsim is specifically for immitating SQL server I\O patterns to stress test your storage solution


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Post #1385384
Posted Thursday, November 15, 2012 7:59 PM


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Sorry, I did mean SQLIO - but for these tests I am only using IOMeter.

Results below for RAID 5
MAX IOPS - uses 4KB transfer request size, 100% reads, 100% sequential dist.:
TOT IO/sec: 121,432
Total MB/sec: 479
Average IO Response Time: 0.13
MAX IO Response 1.85
CPU: 26.5

MAXIOPS with 90% read, 10% write ratio - uses 4KB transfer request size, 90% reads, 10% sequential dist.:
TOT IO/sec: 7000
Total MB/sec: 90
Average IO Response Time: 2.28
MAX IO Response 37.2
CPU: 27.6

I am very surprised with the outcome of the RAID 10, as I thought the performance would be slower:
MAX IOPS - uses 4KB transfer request size, 100% reads, 100% sequential dist.:
TOT IO/sec: 69,445
Total MB/sec: 271
Average IO Response Time: 0.23
MAX IO Response 10.77
CPU: 13.08

MAXIOPS with 90% read, 10% write ratio - uses 4KB transfer request size, 90% reads, 10% sequential dist.:
TOT IO/sec: 23,565
Total MB/sec: 92
Average IO Response Time: 0.68
MAX IO Response 49.9
CPU: 3.02

So it would seem to me that in a RAID5, the more writes you have, you lose IOPS due to the performance hit of maintaining parity across the disks, the main benefits of a RAID 5 would be if and only if you could be sure the writes were kept to an absolute minimum or for a read only file altogether.

At our company, we will have replicated data being written to this new storage array (along with other minor writes from custom tables used for reporting, etc)...so I would think that we wouls ee the best performance in keeping this new array a RAID 10.

Would you agree with this?


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Post #1385431
Posted Friday, November 16, 2012 5:38 AM


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you need to benchmark for a little more than 4KB sequential even for the T-log. Test for the following

8KB random read and write
4-60KB sequential write
64KB sequential read and write
up to 128KB sequential write
up to256KB sequential read

Despite the advances in RAID5 i would expect a well defined RAID10 array to have superior write performance. I'm sure others will jump in here.


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Post #1385626
Posted Friday, November 16, 2012 5:45 AM


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Again as mentioned above this storage array will only be used for data and index files (NO log or tempdb files)

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Post #1385631
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