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Benchmarking Linux filesystems on software RAID 1

by Sander Marechal

A couple of months ago I got a couple of wonderful birthday presents. My lovely geeky girlfriend got me two Western Digital 500 GB SATA 3.0 drives, which were promptly supplemented with a 3ware 9550XS 4-port hardware RAID card. Immediately I came up with the idea for this article. I had just read up on mdadm software RAID (updated reference) so I though it would be perfect to bench mark the hardware RAID against the software RAID using all kinds of file systems, block sizes, chunk sizes, LVM settings, etcetera.

Or so I though… As it turns out, my (then) limited understanding of RAID and some trouble with my 3ware RAID cards meant that I had to scale back my benchmark quite a bit. I only have two disks so I was going to test RAID 1. Chunk size is not a factor when using RAID 1 so that axis was dropped from my benchmark. Then I found out that LVM (and the size of the extends it uses) are also not a factor, so I dropped another axis. And to top it off I discovered some nasty problems with 3ware 9550 RAID cards under Linux that quickly made me give up on hardware RAID. I still ended up testing various filesystems using different blocksizes and workloads on an mdadm RAID 1 setup, so the results should still prove interesting.

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