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According to

For example SAS disks provide ~200 IOPS each.

For RAID 10 consisting of 4 such disks.

How much IOPS I could expect for that array?

I would think it would be about 400 or is it 800? (800 especially in reads? and lower on writes?)

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How many IOPs a certain drive can sustain has more to do with its rotational speed than it does with what protocol it uses. You can get 7.2k SAS drives that will most certainly not crank out 200 IOPs. – EEAA Feb 29 '12 at 20:10
@ErikA at this moment it doesn't matter 7.2k or 15k etc. 200 is just as an example. But I have slightly changed the question. – bakytn Feb 29 '12 at 20:14
up vote 6 down vote accepted

The exact number, or even a reasonable estimate, would be impossible to guess based on this information. Many server grade disks have published number; but the RAID system may or may not take full advantage of the disks. The RAID HBAs generally also have some published benchmarks. Extrapolating from these is the best guess you'll get without testing an actual setup.

So while a a theoretical setup with 4 disks each capable of 200 IOps could sustain 800 IOps Read and 400 IOps Write, the actual number would be less, and might be significantly less.

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