On Sat, 10 Feb 2007, Eyal Lebedinsky wrote:
I have a six-disk RAID5 over sata. First two disks are on the mobo and last four are on a Promise SATA-II-150-TX4. The sixth disk was added recently and I decided to run a 'check' periodically, and started one manually to see how long it should take. Vanilla 2.6.20. A 'dd' test shows: # dd if=/dev/md0 of=/dev/null bs=1024k count=10240 10240+0 records in 10240+0 records out 10737418240 bytes transferred in 84.449870 seconds (127145468 bytes/sec) This is good for this setup. A check shows: $ cat /proc/mdstat Personalities : [raid6] [raid5] [raid4] md0 : active raid5 sda1[0] sdf1[5] sde1[4] sdd1[3] sdc1[2] sdb1[1] 1562842880 blocks level 5, 256k chunk, algorithm 2 [6/6] [UUUUUU] [>....................] check = 0.8% (2518144/312568576) finish=2298.3min speed=2246K/sec unused devices: <none> which is an order of magnitude slower (the speed is per-disk, call it 13MB/s for the six). There is no activity on the RAID. Is this expected? I assume that the simple dd does the same amount of work (don't we check parity on read?). I have these tweaked at bootup: echo 4096 >/sys/block/md0/md/stripe_cache_size blockdev --setra 32768 /dev/md0 Changing the above parameters seems to not have a significant effect. The check logs the following: md: data-check of RAID array md0 md: minimum _guaranteed_ speed: 1000 KB/sec/disk. md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for data-check. md: using 128k window, over a total of 312568576 blocks. Does it need a larger window (whatever a window is)? If so, can it be set dynamically? TIA -- Eyal Lebedinsky (eyal@xxxxxxxxxxxxxx) <http://samba.org/eyal/> attach .zip as .dat - 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
As you add disks onto the PCI bus it will get slower. For 6 disks you should get faster than 2MB/s however..
You can try increasing the min speed of the raid rebuild. Justin. - 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