Re: dirty chunks on bitmap not clearing (RAID1)

I have the same problem.  3 chunks are always dirty.

I'm using 2.6.38-8-generic and mdadm - v3.1.4 - 31st August 2010

If that's not normal, then maybe what I've done differently is that I
created the array, raid 1, with one live and one missing disk, then
added the second one later after writing a lot of data.

Also, though probably not the cause, I continued writing data while it
was syncing, and a couple times during the syncing, both drives
stopped responding and I had to power off.

# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
[raid4] [raid10]
md127 : active raid1 sdd1[0] sdc1[2]
      1904568184 blocks super 1.2 [2/2] [UU]
      bitmap: 3/15 pages [12KB], 65536KB chunk

unused devices: <none>

# mdadm -X /dev/sd[dc]1
        Filename : /dev/sdc1
           Magic : 6d746962
         Version : 4
            UUID : 43761dc5:4383cf0f:41ef2dab:43e6d74e
          Events : 40013
  Events Cleared : 40013
           State : OK
       Chunksize : 64 MB
          Daemon : 5s flush period
      Write Mode : Allow write behind, max 256
       Sync Size : 1904568184 (1816.34 GiB 1950.28 GB)
          Bitmap : 29062 bits (chunks), 3 dirty (0.0%)
        Filename : /dev/sdd1
           Magic : 6d746962
         Version : 4
            UUID : 43761dc5:4383cf0f:41ef2dab:43e6d74e
          Events : 40013
  Events Cleared : 40013
           State : OK
       Chunksize : 64 MB
          Daemon : 5s flush period
      Write Mode : Allow write behind, max 256
       Sync Size : 1904568184 (1816.34 GiB 1950.28 GB)
          Bitmap : 29062 bits (chunks), 3 dirty (0.0%)


Quoting NeilBrown [off-list ref]:

On Thu, October 15, 2009 9:39 am, aristizb@ualberta.ca wrote:

quoted

Hello,

I have a RAID1 with 2 LVM disks and I am running into a strange
situation where having the 2 disks connected to the array the bitmap
never clears the dirty chunks.

That shouldn't happen...
What versions of mdadm and the Linux kernel are you using?

NeilBrown

quoted

I am assuming also that when a RAID1 is in write-through mode, the
bitmap  indicates that all the data has made it to all the disks if
there are no dirty chunks using mdadm --examine-bitmap.

The output of cat /proc/mdstat is:

md2060 : active raid1 dm-5[1] dm-6[0]
       2252736 blocks [2/2] [UU]
       bitmap: 1/275 pages [12KB], 4KB chunk, file: /tmp/md2060bm


The output of mdadm --examine-bitmap /tmp/md2060bm is:

Filename : md2060bm
            Magic : 6d746962
          Version : 4
             UUID : ad5fb74c:bb1c654a:087b2595:8a5d04a9
           Events : 12
   Events Cleared : 12
            State : OK
        Chunksize : 4 KB
           Daemon : 5s flush period
       Write Mode : Normal
        Sync Size : 2252736 (2.15 GiB 2.31 GB)
           Bitmap : 563184 bits (chunks), 3 dirty (0.0%)


Having the array under no IO, I waited 30 minutes but the dirty data
never gets clear from the bitmap, so I presume  the disks are not in
sync; but after I ran a block by block comparison of the two devices I
found that they are equal.

The superblocks and the external bitmap tell me that all the events
are cleared, so I am confused on why the bitmap never goes to 0 dirty
chunks.

How can I tell if the disks are in sync?


Thank you in advance for any help