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[SOLVED] mdadm oddity
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Vieri
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Posts: 546

PostPosted: Sat Feb 11, 2017 9:59 pm    Post subject: [SOLVED] mdadm oddity Reply with quote

Hi,

What does this mean?

Code:
mdadm: /dev/sda3 appears to contain an ext2fs file system
       size=524224K  mtime=Thu Jan  1 00:00:00 1970
mdadm: /dev/sdb3 appears to contain an ext2fs file system
       size=524224K  mtime=Thu Jan  1 00:00:00 1970
mdadm: size set to 524224K
mdadm: creation continuing despite oddities due to --run
mdadm: array /dev/md3 started.


Code:
mdadm: /dev/sda5 appears to contain an ext2fs file system
       size=196241920K  mtime=Sat Feb 11 22:30:34 2017
mdadm: /dev/sdb5 appears to contain an ext2fs file system
       size=196241920K  mtime=Sat Feb 11 22:30:34 2017
mdadm: size set to 196241920K
mdadm: automatically enabling write-intent bitmap on large array
mdadm: creation continuing despite oddities due to --run
mdadm: array /dev/md5 started.


Why does mdadm report an oddity?
/dev/sd{a,b}3 are ext2
/dev/sd{a,b}5 are ext4

Why is ext2fs an "oddity"?

I do find the mtime on /dev/sd{a,b}3 to be odd, though.


Last edited by Vieri on Sun Feb 12, 2017 10:04 am; edited 1 time in total
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Fitzcarraldo
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PostPosted: Sun Feb 12, 2017 1:01 am    Post subject: Reply with quote

Is the 'oddity' only that the partition is already formatted? If you do not use the '--run' option, does mdadm omit any mention of 'oddities' and just prompt you for confirmation to continue?:

Code:
mdadm: /dev/sda3 appears to contain an ext2fs file system
       size=524224K  mtime=Thu Jan  1 00:00:00 1970
mdadm: /dev/sdb3 appears to contain an ext2fs file system
       size=524224K  mtime=Thu Jan  1 00:00:00 1970
Continue creating array?

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Vieri
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PostPosted: Sun Feb 12, 2017 10:04 am    Post subject: Reply with quote

yes, the partition was already formatted, so I guess it's just warning me about that.
I don't know why it should consider it as an oddity, though.

True, without --run, it doesn't mention any oddities but does ask for confirmation.

So I guess it's OK to say "yes" or use --run in this case.

Thanks
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NeddySeagoon
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PostPosted: Sun Feb 12, 2017 11:25 am    Post subject: Reply with quote

Vieri,

What does
Code:
mdadm -E /dev/sda3
show?
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Vieri
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PostPosted: Mon Feb 13, 2017 1:38 pm    Post subject: Reply with quote

Code:
root@sysresccd /root % mdadm -E /dev/sda3
/dev/sda3:
          Magic : a92b4efc
        Version : 0.90.00
           UUID : 4874966d:031521b4:c44c77eb:7ee19756 (local to host sysresccd)
  Creation Time : Mon Feb 13 14:17:32 2017
     Raid Level : raid1
  Used Dev Size : 524224 (511.94 MiB 536.81 MB)
     Array Size : 524224 (511.94 MiB 536.81 MB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 3

    Update Time : Mon Feb 13 14:24:24 2017
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
       Checksum : e92e9884 - correct
         Events : 18


      Number   Major   Minor   RaidDevice State
this     0       8        3        0      active sync   /dev/sda3

   0     0       8        3        0      active sync   /dev/sda3
   1     1       8       19        1      active sync   /dev/sdb3


Looks good.
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NeddySeagoon
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PostPosted: Mon Feb 13, 2017 1:53 pm    Post subject: Reply with quote

Vieri,

As its a raid1, the partition contains a normal filesystem.
With it being a Version : 0.90.00 raid superblock, the filesystem is in the usual place at the start of the partition, with the raid metadata at the end.
mdadm is warning that it can see the normal filesystem.

Don't do this - unless something breaks really badly but you could mount /dev/sda3 directly with the mount command.
The raid metadata would be ignored.
Once you do this, and write to the filesystem, mdadm can't tell its been changed. With a journalled filesystem, ever a read only mount can cause a journal replay and writes.

With version 1.2 raid metadata, the metadata is at the start of the partition and the filesystem follows.
The normal simple mount command fails - it looks in the wrong place for the filesystem.

Your oddity is nothing to worry about.
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NeddySeagoon

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Vieri
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PostPosted: Tue Feb 14, 2017 10:25 am    Post subject: Reply with quote

Thanks for clearing that out!
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