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RAID performance measuring - small files

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Antoine Durr
RAID performance measuring - small files
on Mar 22, 2011 at 9:41:44 am


Is there a tool similar to AJA's diskwhacktest that is better at measuring small file sizes? The disk performance testing seems to favor files over 512KB, very quickly going into multi-gigabyte file sizes, of which, frankly, I have very few. I'd like to test the performance of my RAID setup with files smaller than that (it's going to act as a NAS).

A bit of background: I'm in the process of adding storage to my small (5 Mac Pro) network. Just bought a Sans Digital TR8X-B, which comes with a RocketRaid 2722 card. The downside of the RR2722 is that it only supports RAID5, but with the long rebuild times (41 hours for 8 1.5TB drives), the requirement is really RAID6. To that end, I ran the AJA test suite, and then switched to an ATTO R680 card that I bought (ostensibly for another purpose).

Both cards run roughly at the same speed at the limit. That is, large files get throughputs in the 600 MB/sec write and 700 MB/sec read range. RAID6 on the R680 is about as fast as RAID5 on the RR2722. But... it's at the other end that things get interesting.

Doing a AJA file size sweep on the RR2722 showed pretty poor performance on first point or two of the graph (sub 100MB/sec). The R680, on the other hand, smoked the RR2722 on the small file size end. I'm guessing the R680 takes advantage of burst speeds on the drives to go beyond the 100-120 MB/sec/drive, closer to the 200 MB/sec burst ratings. Thus I saw numbers over 1000MB/sec for 128k file sizes on the R680.

So that is the area I want to better explore. There were some odd dips in the graph that I want to further explore, and as I mentioned, by quantity, more of my files are under 2 MB, though by size, more are 30MB.


-- Antoine

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Bob Zelin
Re: RAID performance measuring - small files
on Mar 22, 2011 at 2:14:32 pm

bob Zelin

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