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2tb nearline sas drives in md3000, horrible performance
Put a couple of 2TB nearline sas drives (Dell-branded WD drives) into one of our MD3000s for a raid1 array that I don't plan to push too hard. My other arrays run great (15k sas drives) but this one crawls - a single sustained transfer gives ok performance, but trying to run hyper-v VMs on it is atrocious.
Anyone have any ideas on how to improve performance? I went with these drives thinking they would perform better than sata, but now I'm wondering since the sata drives seem to have official firmware updates for the md3000 but these don't.
Thanks,
Wes
Dev Mgr
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October 23rd, 2011 08:00
Nearline SAS really just means "SATA with a SAS PCB/controller on the side".
Nearline SAS is 7200rpm, and therefor is ~80iops and has an average seektime of 10-11ms. This is indeed much less/slower/worse than 15k SAS drives (~150iops and ~4ms seektime).
JOHNADCO
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October 24th, 2011 08:00
I have not tried the 2TB's, but the 1TB sas nearline run pretty well for us. They do seem much better than 1TB SATA.
But even with the 1TB Nearline SAS we have to put a ton of them in a group to get decent performance out of them.
Astara_
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March 30th, 2013 07:00
How many disks? MD3000 up to 15? so that's a RAID 10, right? or did you really
mean 1 large 14G contiguous -sequential partition with the other 14GB mirroring?
That's the worst possible combo.
At least you should be doing RAID10 with 7 pairs of RAID1, then you get parallelism.
Peronally, I'd go for RAID50 3 clusters of 5 disks - 1 parity, 4 data, and the 3 clusters
would be stripped. For reads, you get 12 strips reading, and for writes you get a 25% overhead. If you need higher IOP than throughput, going with 5x3's might give you better IOPs at the expense of throughput. Depends on your
needs. Or go RAID10 and get full duplication. But a RAID1 and no striping?
Is that really what you meant?