Recommended hard drive speed testing software?

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Windows: IOmeter, iPeak, ATTO, HDtune - keep in mind that HDtune is not suitable for RAID arrays
Linux: bonnie, raidtest, rawio, iometer, blogbench, dd, iozone

Generally Linux is the superior benchmarking platform - most easy benchmarks for Windows only test sequential performance which is not that important for most users. Even though they might think otherwise. :p
 

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Yeah there are 32MB and 256MB versions of ATTO; i recommend the 256MB one especially if you are testing RAID or complicated setups. But ATTO is not suitable for large write-back buffers (i.e. Areca) -- it will show fluctuating scores.