On Tue, 20 Jul 2010 19:34:06 -0700
"Michael Li" <michael.li [at] 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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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=3D2
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-----
=46rom: Neil Brown [mailto:neilb [at] suse.de]
Sent: 2010=C4=EA7=D4=C221=C8=D5 11:07
To: Michael Li
Cc: linux-raid [at] 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 [at] netgear.com> wrote:

> Hi ,
>
>
>
> I am using RAID10 far copy 2 by 4 disks, when I removed the first dis=
k
> 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 wil=
l
> 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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