Distribution: Debian testing Hardware Environment: * Asus P4P800 Deluxe * 2x Promise FastTrakS150TX4 * 6x SATA-HDD Software Environment: * vanilla-kernel 2.6.4 * gcc version 3.3.3 (Debian) Problem Description: normal processes block on file access a short time after starting a resynchronisation of a RAID-1 Steps to reproduce: * /boot is on /dev/md0 * / is on /dev/md1 * create (50GB) RAID-1 with "mdadm --create /dev/md1 --level=raid1 --raid-disks=2 /dev/sda7 /dev/sdc7" * run (for example) "while [ 1 ]; do clear; cat /proc/mdstat; sleep 1; done"; this will block after a short period of time * pings to and portscans of the RAID-machine still work * after the resynchronization has finished, everything continues as usual This problem does not seem to exist in vanilla kernel 2.6.3
The "/dev/md1" in the "mdadm --create" command is a typo and should be "/dev/md2".
Is this still an issue or can we close this?
I'm sorry, but it's still an issue, as I had to notice last saturday.
1/ May I introduce the progam 'watch' to you? very useful for watching /proc/mdstat. 2/ Could you get me a copy of /proc/mdstat just before it stops responding? 3/ Can you try dd if=/dev/sda7 of=/dev/sdc7 bs=1024k & (to effectively do the copy by hand) and see how responsive the system is while that is happening? (This will ofcourse make a mess of /dev/sdc7, don't do it if you value the data there). Thanks, NeilBrown
1/ I recently got introduced to watch, but thank you for the hint. =;) 3/ ok, let's see: $ sudo mdadm /dev/md2 -r /dev/sde7 $ sudo dd bs=1024k if=/dev/sda7 of=/dev/sde7 This is not an issue. $ sudo dd bs=1024k if=/dev/sdc7 of=/dev/sde7 This also is not an issue. 2/ $ sudo mdadm /dev/md2 -a /dev/sde7 $ sudo mdadm /dev/md2 -f /dev/sdc7; sudo sudo mdadm /dev/md2 -r /dev/sdc7; sudo mdadm /dev/md2 -a /dev/sdc7 Every 2s: cat /proc/mdstat Tue Oct 11 21:53:19 2005 Personalities : [raid1] [raid5] [raid6] md2 : active raid1 sdc7[2] sde7[3] sda7[0] 51375744 blocks [2/1] [U_] [>....................] recovery = 0.2% (130048/51375744) finish=19.6min speed=43349K/sec md4 : active raid1 sde8[2] sdc8[0] sda8[1] 51375744 blocks [2/2] [UU] md6 : active raid1 sdc9[2] sde9[0] sda9[1] 51375744 blocks [2/2] [UU] [...] Every 2s: cat /proc/mdstat Tue Oct 11 22:08:59 2005 Personalities : [raid1] [raid5] [raid6] md2 : active raid1 sdc7[2] sde7[3] sda7[0] 51375744 blocks [2/1] [U_] [============>........] recovery = 60.5% (31095168/51375744) finish=8.0mi n speed=41885K/sec [...] This is an issue. The cat blocks on reading /proc/mdstat often for several seconds sometimes up to some minutes. Access to the filesystems also blocks during that. BTW: All this is not an issue on another machine, which has 2 IDE drives and is running kernel 2.4.27.
The problem does not seem to exist any longer when using the cfq I/O scheduler instead of the anticipatory i/o scheduler.
Hans-Peter, Does this sufficiently resolve the problem for you? Is this still true with current kernel? Then we can close this bug, if no objections. Thanks.
Hello Natalie, yes, this workaround solves the problem for me. Best regards, Hans-Peter
Closing the bug. If someone objects and wishes to look more into scheduler, please reopen.