More updates:
1. I upgraded to openSUSE 11.1 over the weekend. The kernel is
2.6.27.7-9 as of this writing.
2. When I fired up the machine which hosts the network block device,
the machine hosting the raid properly noticed and --re-added /dev/nbd0
to /dev/md11.
3. /dev/md11 went into "recover" mode (not resync).
4. I'm using persistent metadata and a write-intent bitmap.
**Question**:
What am I doing wrong here? Why doesn't --re-add cause resync instead
of rebuild? If I'm reading the output from --examine-bitmap (below)
correctly, there are 2049 dirty bits at 4MB per bit or about 8196 MB
to resync.
According to this (from the manpage)
If an array is using a write-intent bitmap, then devices
which have been removed can be re-added in a way that
avoids a full reconstruction but instead just updates
the blocks that have changed since the device was
removed. For arrays with persistent metadata
(superblocks) this is done automatically. For arrays
created with --build mdadm needs to be told that this
device we removed recently with --re-add.
I'm doing everything OK.
I can the --examine, --examine-bitmap from /dev/nbd0 *before* it is
added to the array:
Magic : a92b4efc
Version : 1.0
Feature Map : 0x1
Array UUID : cf24d099:9e174a79:2a2f6797:dcff1420
Name : turnip:11 (local to host turnip)
Creation Time : Mon Dec 15 07:06:13 2008
Raid Level : raid1
Raid Devices : 2
Avail Dev Size : 160086384 (76.34 GiB 81.96 GB)
Array Size : 156247976 (74.50 GiB 80.00 GB)
Used Dev Size : 156247976 (74.50 GiB 80.00 GB)
Super Offset : 160086512 sectors
State : clean
Device UUID : 01524a75:c309869c:6da972c9:084115c6
Internal Bitmap : 2 sectors from superblock
Flags : write-mostly
Update Time : Sat Dec 20 19:43:43 2008
Checksum : 63c19462 - correct
Events : 7042
Array Slot : 2 (failed, failed, empty, 1)
Array State : _u 2 failed
Filename : /dev/nbd0
Magic : 6d746962
Version : 4
UUID : cf24d099:9e174a79:2a2f6797:dcff1420
Events : 5518
Events Cleared : 5494
State : OK
Chunksize : 4 MB
Daemon : 5s flush period
Write Mode : Allow write behind, max 256
Sync Size : 78123988 (74.50 GiB 80.00 GB)
Bitmap : 19074 bits (chunks), 0 dirty (0.0%)
Then I --re-added /dev/nbd0 to the array:
Dec 22 08:15:53 turnip kernel: RAID1 conf printout:
Dec 22 08:15:53 turnip kernel: --- wd:1 rd:2
Dec 22 08:15:53 turnip kernel: disk 0, wo:1, o:1, dev:nbd0
Dec 22 08:15:53 turnip kernel: disk 1, wo:0, o:1, dev:sda
Dec 22 08:15:53 turnip kernel: md: recovery of RAID array md11
Dec 22 08:15:53 turnip kernel: md: minimum _guaranteed_ speed: 1000
KB/sec/disk.
Dec 22 08:15:53 turnip kernel: md: using maximum available idle IO
bandwidth (but not more than 5120 KB/sec) for recovery.
Dec 22 08:15:53 turnip kernel: md: using 128k window, over a total of
78123988 blocks.
And this is what things look like 20 minutes into the reconstruction/rebuild:
turnip:~ # mdadm --examine-bitmap /dev/sda
Filename : /dev/sda
Magic : 6d746962
Version : 4
UUID : cf24d099:9e174a79:2a2f6797:dcff1420
Events : 15928
Events Cleared : 5494
State : OK
Chunksize : 4 MB
Daemon : 5s flush period
Write Mode : Allow write behind, max 256
Sync Size : 78123988 (74.50 GiB 80.00 GB)
Bitmap : 19074 bits (chunks), 2065 dirty (10.8%)
turnip:~ # mdadm --examine-bitmap /dev/nbd0
Filename : /dev/nbd0
Magic : 6d746962
Version : 4
UUID : cf24d099:9e174a79:2a2f6797:dcff1420
Events : 5518
Events Cleared : 5494
State : OK
Chunksize : 4 MB
Daemon : 5s flush period
Write Mode : Allow write behind, max 256
Sync Size : 78123988 (74.50 GiB 80.00 GB)
Bitmap : 19074 bits (chunks), 0 dirty (0.0%)
turnip:~ #
and finally some --detail:
/dev/md11:
Version : 1.00
Creation Time : Mon Dec 15 07:06:13 2008
Raid Level : raid1
Array Size : 78123988 (74.50 GiB 80.00 GB)
Used Dev Size : 156247976 (149.01 GiB 160.00 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Mon Dec 22 08:24:25 2008
State : active, degraded, recovering
Active Devices : 1
Working Devices : 2
Failed Devices : 0
Spare Devices : 1
Rebuild Status : 8% complete
Name : turnip:11 (local to host turnip)
UUID : cf24d099:9e174a79:2a2f6797:dcff1420
Events : 15928
Number Major Minor RaidDevice State
2 43 0 0 writemostly spare rebuilding /dev/nbd0
3 8 0 1 active sync /dev/sda
--
Jon
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