Hello -
I hope some kind soul is able to help. I have configured a RAID1 array - two mirrored drives, one spare. My understanding is that the spare disk should be allowed to spin down, but it won't.
When I searched for troubleshooting information, I found talk of work that had been done specifically to allow the spare to spin down - to do with decrementing the event counter instead of incrementing it. So, I'm surprised this doesn't seem to be working in my case.
If I poll /proc/diskstats, I see writes to the spare drive (sdb1) every few seconds.
If I remove the drive from the RAID array, the writes stop and it is able to spin down.
If I do "mdadm --examine /dev/sdb1", I can see the event counter is increasing every two or three seconds.
The kernel is 2.6.32-21-generic - a new Ubuntu 10.04 install.
/proc/mdstat yields:
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb1[2](S) sda1[0](W) sdc1[1]
29295552 blocks [2/2] [UU]
md1 : active raid1 sdb5[2](S) sda5[0](W) sdc5[1]
1951680 blocks [2/2] [UU]
unused devices: <none>
Other facts that I don't think should be relevant but you may know better:
- You can see that in fact I have two RAID arrays - md0 is the
troublesome one.
- md0 contains LVM, which contains ext4, which contains root filesystem.
- sdc is an SSD drive. sda and sdb are spinning disks.
- If I do "cat /sys/block/md0/md/safe_mode_delay" I get "0.210".
- I briefly had write-intent bitmaps set up for both md0 and md1, but I have since removed them.
This box is a fresh build and can be rebuilt if that's necessary to fix
or diagnose the problem.
Thanks in advance for any help. Linux software RAID is just terrific - I report this minor issue largely because, as I said, it seems like this is something that is *supposed* to work.
--
Joe Bryant
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