>From: GuoZhong Han
>Date: 2012-10-10 19:15
>To: linux-raid
>Subject: hotunpluged a disk, raid5 disappeared after reboot
>Hello, every one:
>I had a 4*2T (sdh, sdi, sdj,sdk)raid5 with 128K chuck size and 2048
>strip_cache_size. The mdadm 3.2.2, kernel 2.6.38 were used. I wrote a
>program to test the write performance for the raid5. While the program
>was writing data to the raid5, I unplugged sdk, then I rebooted the
>machine. After that, I used "mdadm --assemble --scan" to scan the
>array. The output was "bot enough to start the array while not clean -
>consider --force" The array was seemed disappeared. Then I used
>"mdadm -E /dev/sd[ijh]" to check the superblocks of sdi,sdj and sdh,
>the outputs were the following:
># mdadm -E /dev/sd[ijh]
>/dev/sdh:
> Magic : a92b4efc
> Version : 1.2
> Feature Map : 0x0
> Array UUID : c2e5a470:4a7e42c3:96273d8c:1c8ad2b7
> Name : localhost:RAID5 (local to host localhost)
> Creation Time : Mon Sep 10 20:17:15 2012
> Raid Level : raid5
> Raid Devices : 4
> Avail Dev Size : 310344694 (147.98 GiB 158.90 GB)
> Array Size : 931031040 (443.95 GiB 476.69 GB)
> Used Dev Size : 310343680 (147.98 GiB 158.90 GB)
> Data Offset : 2048 sectors
> Super Offset : 8 sectors
> State : active
> Device UUID : 2d86ad25:16130eaf:6da00473:60ba7143
> Update Time : Tue Sep 11 12:18:55 2012
> Checksum : 878b469a - correct
> Events : 108
> Layout : left-symmetric
> Chunk Size : 512K
> Device Role : Active device 0
> Array State : AAA. ('A' == active, '.' == missing)
>/dev/sdi:
> Magic : a92b4efc
> Version : 1.2
> Feature Map : 0x0
> Array UUID : c2e5a470:4a7e42c3:96273d8c:1c8ad2b7
> Name : localhost:RAID5 (local to host localhost)
> Creation Time : Mon Sep 10 20:17:15 2012
> Raid Level : raid5
> Raid Devices : 4
> Avail Dev Size : 310344844 (147.98 GiB 158.90 GB)
> Array Size : 931031040 (443.95 GiB 476.69 GB)
> Used Dev Size : 310343680 (147.98 GiB 158.90 GB)
> Data Offset : 2048 sectors
> Super Offset : 8 sectors
> State : active
> Device UUID : 7f74fb29:1b2c5c03:1e2b8de1:e25c9e39
> Update Time : Tue Sep 11 12:18:55 2012
> Checksum : 44dc7bbb - correct
> Events : 108
> Layout : left-symmetric
> Chunk Size : 512K
> Device Role : Active device 1
> Array State : AAA. ('A' == active, '.' == missing)
>/dev/sdj:
> Magic : a92b4efc
> Version : 1.2
> Feature Map : 0x0
> Array UUID : c2e5a470:4a7e42c3:96273d8c:1c8ad2b7
> Name : localhost:RAID5 (local to host localhost)
> Creation Time : Mon Sep 10 20:17:15 2012
> Raid Level : raid5
> Raid Devices : 4
> Avail Dev Size : 310344346 (147.98 GiB 158.90 GB)
> Array Size : 931031040 (443.95 GiB 476.69 GB)
> Used Dev Size : 310343680 (147.98 GiB 158.90 GB)
> Data Offset : 2048 sectors
> Super Offset : 8 sectors
> State : active
> Device UUID : 5c58dcec:d03b6bd0:738bc5ea:e0c75d33
> Update Time : Tue Sep 11 12:18:55 2012
> Checksum : d7c438b0 - correct
> Events : 108
> Layout : left-symmetric
> Chunk Size : 512K
> Device Role : Active device 2
> Array State : AAA. ('A' == active, '.' == missing)
>As the output of "mdadm --assemble --scan" suggested, I used "mdadm
>assemble --scan --force" to scan the array again. It did work. Again I
>used "mdadm -E /dev/sd[ijh]" to see the superblocks of sdi,sdj and
>sdh, the outputs were the following:
># mdadm -E /dev/sd[ijh]
>/dev/sdh:
> Magic : a92b4efc
> Version : 1.2
> Feature Map : 0x0
> Array UUID : c2e5a470:4a7e42c3:96273d8c:1c8ad2b7
> Name : localhost:RAID5 (local to host localhost)
> Creation Time : Mon Sep 10 20:17:15 2012
> Raid Level : raid5
> Raid Devices : 4
> Avail Dev Size : 310344694 (147.98 GiB 158.90 GB)
> Array Size : 931031040 (443.95 GiB 476.69 GB)
> Used Dev Size : 310343680 (147.98 GiB 158.90 GB)
> Data Offset : 2048 sectors
> Super Offset : 8 sectors
> State : clean
> Device UUID : 2d86ad25:16130eaf:6da00473:60ba7143
> Update Time : Tue Sep 11 12:18:55 2012
> Checksum : 878b469a - correct
> Events : 108
> Layout : left-symmetric
> Chunk Size : 512K
> Device Role : Active device 0
> Array State : AAA. ('A' == active, '.' == missing)
>/dev/sdi:
> Magic : a92b4efc
> Version : 1.2
> Feature Map : 0x0
> Array UUID : c2e5a470:4a7e42c3:96273d8c:1c8ad2b7
> Name : localhost:RAID5 (local to host localhost)
> Creation Time : Mon Sep 10 20:17:15 2012
> Raid Level : raid5
> Raid Devices : 4
> Avail Dev Size : 310344844 (147.98 GiB 158.90 GB)
> Array Size : 931031040 (443.95 GiB 476.69 GB)
> Used Dev Size : 310343680 (147.98 GiB 158.90 GB)
> Data Offset : 2048 sectors
> Super Offset : 8 sectors
> State : active
> Device UUID : 7f74fb29:1b2c5c03:1e2b8de1:e25c9e39
> Update Time : Tue Sep 11 12:18:55 2012
> Checksum : 44dc7bbb - correct
> Events : 108
> Layout : left-symmetric
> Chunk Size : 512K
> Device Role : Active device 1
> Array State : AAA. ('A' == active, '.' == missing)
>/dev/sdj:
> Magic : a92b4efc
> Version : 1.2
> Feature Map : 0x0
> Array UUID : c2e5a470:4a7e42c3:96273d8c:1c8ad2b7
> Name : localhost:RAID5 (local to host localhost)
> Creation Time : Mon Sep 10 20:17:15 2012
> Raid Level : raid5
> Raid Devices : 4
> Avail Dev Size : 310344346 (147.98 GiB 158.90 GB)
> Array Size : 931031040 (443.95 GiB 476.69 GB)
> Used Dev Size : 310343680 (147.98 GiB 158.90 GB)
> Data Offset : 2048 sectors
> Super Offset : 8 sectors
> State : active
> Device UUID : 5c58dcec:d03b6bd0:738bc5ea:e0c75d33
> Update Time : Tue Sep 11 12:18:55 2012
> Checksum : d7c438b0 - correct
> Events : 108
> Layout : left-symmetric
> Chunk Size : 512K
> Device Role : Active device 2
> Array State : AAA. ('A' == active, '.' == missing)
>There was basically nothing inconsistent between the two outputs,
>except that the state of "sdh" in the former output was "active"
>while in the latter was "clean"
>What was the problem? Can any one help me?
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