Maurice Hilarius wrote:
A friend writes: On a recent machine set up with Raid5. On a AMD Phenom II X4 810, and 4GB ram. 4 Seagate 7200.12 SATA 1TB drives, I'm getting some rather impressive numbers for sequential read (300MB/s+) and write (170MB/s+) but the random read is proving to be absolutely atrocious. iostat says its going at about 0.5MB/s,
The key thing about random i/o is the block size. With, say, 512bytes blocks and single thread you will see less than 0.5Mb/sec. With 64kbytes blocksize it will be much better. To diagnose: first try the same test on bare disk without raid layer. Next try to vary block size and number of concurrent threads doing I/O. There's no tweaks needed really. /mjt -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
