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Stripe size for 2 SAS disk RAID0?

I

imipenem

Senior member
Can someone recommend the best stripe size for a RAID0 array using two Seagate Cheetah 15K.6 300GB SAS drives on an Areca ARC-1680i controller?

Thanks
 
As large as possible, to accelerate random I/O. Minimum would be 128KiB. You would need more if you have a stripe misalignment; i.e. when using Windows XP or other non-RAID compatible OS that creates partitions at 31.5KiB offset crippling RAID performance.
 
it is really software dependent too. i use online stripe migration to sample the iops/time with the specific application in mind (like sql server).
 
Its mostly dependent on the RAID engine, not the application. Some RAID engines read all data in a stripe block, so if you have 128KiB stripesize and read only 4KiB; the RAID engine reads all. This is very bad of course, and will limit IOps performance. Properly setup striping RAID will cause one I/O request to be handled by only one physical drive, and if your RAID engine doesn't use 'optimization tricks' that actually lower performance, you can safely use stripesizes of multiple megabytes in size; for maximum random IOps performance.
 
128KB works best with these controllers. I've been using these controllers since they came out with various SAS disks (mostly Fujitsu MAX and MBA series) and 128KB gives consistently the best results. (tested with iometer)
 
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