On Mon, 5 Dec 2011 08:49:03 +0100 Vincent Pelletier <plr.vincent@xxxxxxxxx> wrote: > On Mon, Dec 5, 2011 at 7:11 AM, NeilBrown <neilb@xxxxxxx> wrote: > > 5 seconds suggests a bitmap update. Do you have an internal bitmap? > > I don't, but I enabled it on those arrays before with default delay. > I then removed it when I suspected (with help of block_dump) it to > cause spin-ups, and I noticed an improvement. Recently, the machine > was restarted (once on 3.0 kernel, and again to update to 3.1), and > after both restarts those 5s periodic writes occurred. > > > Then try adding it back with a longer delay > > mdadm --grow /dev/md0 --bitmap=internal --delay=60 > > Adding bitmaps on both arrays (md0 and md1), 5s periodic writes disappear. > Removing bitmaps seems to preserve the improvement. > > Could the delay setting have survived on-disk and be used when > initializing the array, but cleared when mdadm later disables bitmap > usage ? > > > What kernel version are you running? > > 3.1.4, according to dpkg: > ii linux-image-3.1.0-1-amd64 3.1.4-1 > Linux 3.1 for 64-bit PCs > > Regards, Hmm... I cannot reproduce this which makes it harder. Can you enable dynamic debugging on md? Make sure CONFIG_DYNAMIC_DEBUG is set, mount debugfs on /sys/kernel/debug and echo module md_mod +p > /sys/kernel/debug/dynamic_debug/control then look for extra messages in the kernel logs, starting "md:" most likely. You'll almost certainly see something like [ 1851.559629] md: waking up MD thread md0_raid1. [ 1851.625819] md: updating md0 RAID superblock on device (in sync 1) [ 1851.656878] md: (write) sdb's sb offset: 8 [ 1851.656915] md: (write) sda's sb offset: 8 every 5 seconds. If you could confirm that and report if there is anything else reported that might help. NeilBrown
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