Re: RAID10 status when you remove the first disk and last disk

Re: RAID10 status when you remove the first disk and last disk

[Neil Brown]

On Tue, 20 Jul 2010 19:34:06 -0700
"Michael Li" <michael.li@netgear.com> wrote:

> Hi ,
> 
>  
> 
> I am using RAID10 far copy 2 by 4 disks, when I removed the first disk
> and last disk, I think this raid should be failed, but mdadm -D
> /dev/md2, I saw it was degraded, but when I try to read/write, there
> will be I/O error. And when I added the two disks again, the raid will
> be recovery, so that's normal? why it is designed like this?
> 
>  
> 
> Anyone know the detail about that? Thanks so much!
> 

Sounds like a bug.  You have definitely lost data if the first and last
devices of such an array go missing, so it should not try to recover a spare
in to either slot.

What kernel version are you using?

NeilBrown

RE: RAID10 status when you remove the first disk and last disk

[Michael Li]

Thanks for your attention.
I am using version 2.6.33.4
# mdadm -D /dev/md2
/dev/md2:
        Version : 1.2
  Creation Time : Tue Jul 20 00:17:31 2010
     Raid Level : raid10
     Array Size : 7401216 (7.06 GiB 7.58 GB)
  Used Dev Size : 3700608 (3.53 GiB 3.79 GB)
   Raid Devices : 4
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Tue Jul 20 22:34:12 2010
          State : clean, degraded
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

         Layout : far=2
     Chunk Size : 64K

           Name : 001F33EA1487:2
           UUID : 58fa65b1:36791e6c:708a49d6:e458fe4e
         Events : 698

    Number   Major   Minor   RaidDevice State
       0       0        0        0      removed
       1       8       19        1      active sync   /dev/sdb3
       2       8       35        2      active sync   /dev/sdc3
       3       0        0        3      removed

-----Original Message-----
From: Neil Brown [mailto:neilb@suse.de] 
Sent: 2010年7月21日 11:07
To: Michael Li
Cc: linux-raid@vger.kernel.org
Subject: Re: RAID10 status when you remove the first disk and last disk

On Tue, 20 Jul 2010 19:34:06 -0700
"Michael Li" <michael.li@netgear.com> wrote:

> Hi ,
> 
>  
> 
> I am using RAID10 far copy 2 by 4 disks, when I removed the first disk
> and last disk, I think this raid should be failed, but mdadm -D
> /dev/md2, I saw it was degraded, but when I try to read/write, there
> will be I/O error. And when I added the two disks again, the raid will
> be recovery, so that's normal? why it is designed like this?
> 
>  
> 
> Anyone know the detail about that? Thanks so much!
> 

Sounds like a bug.  You have definitely lost data if the first and last
devices of such an array go missing, so it should not try to recover a spare
in to either slot.

What kernel version are you using?

NeilBrown

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