I'm running Debian sarge on a system with two IDE drives. I used the
installer to create a mirrored filesystem on the first partition of both
discs and it's mounted as the root; everything was working fine.
Unfortunately, I noticed the two devices were on the same IDE channel
(i.e. /dev/hda1 and /dev/hdb1), so I moved them on to different channels
(/dev/hda1 and /dev/hdc1). Now, the array only finds the one device when
it starts up (/dev/hda1). In case it's relevant, because of the cable
lengths the drives moved as follows:
dev/hda -> dev/hdc
dev/hdb -> dev/hda
I believe all I really need to do is update the superblock on /dev/hda1
so the md driver knows to look at /dev/hdc1 rather than /dev/hdb1.
Unfortunately, I can't work out how to do this. The only references I've
seen to rewriting the superblock is with mdadm --assemble, but I can't
use that because it's already running.
I've tried removing both drives from the array (not at the same time, of
course), then re-adding them and waiting for it to finish syncing, but
that doesn't help. After a reboot, I still get the same problem. In
fact, now it looks like it's not even trying /dev/hdb1; it looks like it
recorded the fact I had removed the drive, but not the fact I'd added it
again.
After using mdadm --manage /dev/md0 --add /dev/hdc1 and waiting for the
array to resync, the superblock info on both discs match.
Below is the current situation in terms of mdadm output, after re-adding
/dev/hdc1 to /dev/md0 and waiting for it to resync. (md1 is on hda1 and
hdc1, and has the same problem.)
# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 hda3[1]
9767424 blocks [2/1] [_U]
md0 : active raid1 hdc1[0] hda1[1]
2441728 blocks [2/2] [UU]
unused devices: <none>
The superblocks look correct to me, as the following shows:
# mdadm --misc --examine /dev/hda1
/dev/hda1:
Magic : a92b4efc
Version : 00.90.00
UUID : d2b494fc:a181e190:a09f1dfb:b226ea79
Creation Time : Tue Jan 10 15:53:02 2006
Raid Level : raid1
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Update Time : Wed Jan 11 13:10:10 2006
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Checksum : f7d5252c - correct
Events : 0.3266
Number Major Minor RaidDevice State
this 1 3 1 1 active sync /dev/hda1
0 0 22 1 0 active sync /dev/hdc1
1 1 3 1 1 active sync /dev/hda1
# mdadm --misc --examine /dev/hdc1
/dev/hdc1:
(I removed the status information here to make it more readable; it is
identical for both devices, so it looks like they are properly
synchronized.)
Number Major Minor RaidDevice State
this 0 22 1 0 active sync /dev/hdc1
0 0 22 1 0 active sync /dev/hdc1
1 1 3 1 1 active sync /dev/hda1
After a reboot:
# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 hda3[1]
9767424 blocks [2/1] [_U]
md0 : active raid1 hda1[1]
2441728 blocks [2/1] [_U]
unused devices: <none>
# mdadm --misc --examine /dev/hda1
/dev/hda1:
Magic : a92b4efc
Version : 00.90.00
UUID : d2b494fc:a181e190:a09f1dfb:b226ea79
Creation Time : Tue Jan 10 15:53:02 2006
Raid Level : raid1
Raid Devices : 2
Total Devices : 1
Preferred Minor : 0
Update Time : Wed Jan 11 13:17:37 2006
State : clean
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0
Checksum : f7d5275f - correct
Events : 0.3336
Number Major Minor RaidDevice State
this 1 3 1 1 active sync /dev/hda1
0 0 0 0 0 removed
1 1 3 1 1 active sync /dev/hda1
# mdadm --misc --examine /dev/hdc1
/dev/hdc1:
Magic : a92b4efc
Version : 00.90.00
UUID : d2b494fc:a181e190:a09f1dfb:b226ea79
Creation Time : Tue Jan 10 15:53:02 2006
Raid Level : raid1
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Update Time : Wed Jan 11 13:12:00 2006
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Checksum : f7d525d7 - correct
Events : 0.3288
Number Major Minor RaidDevice State
this 0 22 1 0 active sync /dev/hdc1
0 0 22 1 0 active sync /dev/hdc1
1 1 3 1 1 active sync /dev/hda1
Relevant parts of the boot process:
Kernel command line: root=/dev/md0 ro
hda: ST380011A, ATA DISK drive
Using anticipatory io scheduler
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
hda: max request size: 128KiB
hda: 156301488 sectors (80026 MB) w/2048KiB Cache, CHS=65535/16/63,
UDMA(100)
/dev/ide/host0/bus0/target0/lun0: p1 p2 p3 p4 < p5 p6 >
hdc: ST380011A, ATA DISK drive
ide1 at 0x170-0x177,0x376 on irq 15
hdc: max request size: 128KiB
hdc: 156301488 sectors (80026 MB) w/2048KiB Cache, CHS=65535/16/63,
UDMA(100)
/dev/ide/host0/bus1/target0/lun0: p1 p2 p3 p4 < p5 p6 >
md: md0 stopped.
md: bind<hda1>
raid1: raid set md0 active with 1 out of 2 mirrors
Any suggestions would be greatly appreciated. The system's new and not
yet in production, so I can reinstall it if I have to, but I'd prefer to
be able to fix something as simple as this.
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