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@xxxxxxx] Sent: 2010年7月21日 11:07 To: Michael Li Cc: linux-raid@xxxxxxxxxxxxxxx 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@xxxxxxxxxxx> 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 This e-mail, including attachments, may include confidential and/or proprietary information, and may be used only by the person or entity to which it is addressed. If the reader of this e-mail is not the intended recipient or his or her authorized agent, the reader is hereby notified that any dissemination, distribution or copying of this e-mail is prohibited. If you have received this e- mail in error, please notify the sender by replying to this message and delete this e-mail immediately -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html