Neil Brown a écrit :
On Wednesday October 21, stephane.bunel@xxxxxxxxxxxxxxxxx wrote:
Hi,
I'm a newbie in the mdadm world. I defined some udev rules to make disk
staticly named according to the bus/host/target. I.e. /dev/sda become
/dev/raid_disk0. So nothing very special with that, it's just a convenient way
to assign disk name to it's physical location.
#ls -la /dev/raid*
brw-rw---- 1 root disk 8, 0 2009-10-16 18:12 /dev/raid_disk0
brw-rw---- 1 root disk 8, 16 2009-10-16 18:12 /dev/raid_disk1
A RAID1 (/dev/md0) is assembled over this two disk.
When looking for detailed information, mdadm show annoying device name in
place of /dev/raid_disk*:
....
Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/char/21:0
1 8 16 1 active sync /dev/char/21:1
What is a block device doing in /dev/char ??? There should only be
character devices in there.
If these are actually block device, then I think there is something
wrong with your udev rules.
I think my udev rules are not in cause because they just change /dev/sd* to
/dev/raid_disk*. For udev /dev/char/21:0 seems correspond to the generic scsi
device driver (sg) wich is binded to scsi devices.
If these are char devices, then mdadm is doing the wrong thing, but I
cannot see that from the code.
mdadm by choosing the shorter name without differentiate path (/dev/.../ )
and name (sda) choose /dev/char/21:0 just because it is shorter than
/dev/raid_disk0.
Your proposal of choosing the highest rather than the shortest name
has some merit, but I your current situation doesn't seem to justify
it, and I particularly like the simplicity of the current heuristic.
My proposal doesn't choose the highest name but does a selection based on
the shortest path to the device name. I.e. my proposal choose:
/dev/raid_disk0 (1 directory level) over /dev/char/21:0 (2 directory level)
/dev/raid_disk0 (1 directory level) over /dev/block/8:0 (2 directory level)
/dev/sda1 (1 directory level) over /dev/disk/by-label/BOOT (3 directory level)
So in fact, my proposal doesn't change current situation but "adjust" the
heuristic to avoid seeing an annoying device name (char device) as a member of
raid just because it's fullname is shorter than a "semantically better" name.
Add a printf in map_dev() show that my proposal seems help the heuristic to
be more robust in case of "advanced" device naming, without changing current
things.
#./mdadm --detail /dev/md0
(/dev/char/21:0)
(/dev/block/8:0)
(/dev/disk/by-id/ata-Hitachi_HDP725050GLA360_GEA534RJ37D3RA)
(/dev/disk/by-id/scsi-SATA_Hitachi_HDP7250_GEA534RJ37D3RA)
(/dev/raid_disk0)
(/dev/char/21:1)
(/dev/block/8:16)
(/dev/raid_disk1)
(/dev/disk/by-id/ata-Hitachi_HDP725050GLA360_GEA534RJ36T9VA)
(/dev/disk/by-id/scsi-SATA_Hitachi_HDP7250_GEA534RJ36T9VA)
/dev/md0:
Version : 0.90
Creation Time : Tue Oct 13 12:53:54 2009
Raid Level : raid1
Array Size : 488386496 (465.76 GiB 500.11 GB)
Used Dev Size : 488386496 (465.76 GiB 500.11 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Thu Oct 22 12:42:44 2009
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
UUID : 3fea95a0:e1b8a341:3b119117:e416f62b
Events : 0.1526
Number Major Minor RaidDevice State
0 8 0 0 active sync(/dev/char/21:0)
(/dev/block/8:0)
(/dev/disk/by-id/ata-Hitachi_HDP725050GLA360_GEA534RJ37D3RA)
(/dev/disk/by-id/scsi-SATA_Hitachi_HDP7250_GEA534RJ37D3RA)
(/dev/raid_disk0)
/dev/raid_disk0
1 8 16 1 active sync(/dev/char/21:1)
(/dev/block/8:16)
(/dev/raid_disk1)
(/dev/disk/by-id/ata-Hitachi_HDP725050GLA360_GEA534RJ36T9VA)
(/dev/disk/by-id/scsi-SATA_Hitachi_HDP7250_GEA534RJ36T9VA)
/dev/raid_disk1
Thanks,
Stéphane Bunel.
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