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Undestanding /proc/mdstat with raid10

DISCUSSION Sebastian Muniz 2 participants 2 messages Aug 9, 2011 MD RAID

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Sebastian Muniz

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#0 lore raw

Hello,
I have searched a lot trying to answer this. I have a raid10 array on an openfiler box. Personalities : [raid10]
md0 : active raid10 sde1[3] sdd1[2] sdc1[1] sdb1[0]

      181760 blocks super 1.2 64K chunks 2 near-copies [4/4] [UUUU]

unused devices: <none>
Actually this is a Virtualbox machine with the same disk setup. I made 6 x 100 Mbytes disks for the test.

How can I tell which disks are mirrored?

My goal is to free the two mirror disks from md0, add two more free disks, create a new md1 raid5 array, and move the contents from md0 to md1

Thanks in advance.
Sebastian

PS: in case it is relevant, i am adding the detailed md0 output.

[root@of ~]# mdadm --misc --detail /dev/md0
/dev/md0:

        Version : 1.2

Creation Time : Tue Aug 9 03:01:14 2011
Raid Level : raid10
Array Size : 181760 (177.53 MiB 186.12 MB)
Used Dev Size : 90880 (88.76 MiB 93.06 MB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent

Update Time : Tue Aug 9 03:20:06 2011
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0

Layout : near=2
Chunk Size : 64K

Name : of:0 (local to host of) UUID : 63b2145a:49030744:41b8f5b4:cb11bc1d
Events : 19

Number Major Minor RaidDevice State
0 8 17 0 active sync /dev/sdb1
1 8 33 1 active sync /dev/sdc1
2 8 49 2 active sync /dev/sdd1
3 8 65 3 active sync /dev/sde1

#1 lore raw
Quoted 5 lines · Sebastian Muniz

Hello,
I have searched a lot trying to answer this. I have a raid10 array on an openfiler box. Personalities : [raid10]
md0 : active raid10 sde1[3] sdd1[2] sdc1[1] sdb1[0]

Quoted 7 lines
       181760 blocks super 1.2 64K chunks 2 near-copies [4/4] [UUUU]

unused devices: <none>
Actually this is a Virtualbox machine with the same disk setup. I made 6 x 100 Mbytes disks for the test.

How can I tell which disks are mirrored?

That depends on the layout of your array. raid10 is not raid1+0

Quoted 20 lines

My goal is to free the two mirror disks from md0, add two more free disks, create a new md1 raid5 array, and move the contents from md0 to md1

Thanks in advance.
Sebastian

PS: in case it is relevant, i am adding the detailed md0 output.

[root@of ~]# mdadm --misc --detail /dev/md0
/dev/md0:

         Version : 1.2

Creation Time : Tue Aug 9 03:01:14 2011
Raid Level : raid10
Array Size : 181760 (177.53 MiB 186.12 MB)
Used Dev Size : 90880 (88.76 MiB 93.06 MB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent

Quoted 8 lines

Update Time : Tue Aug 9 03:20:06 2011
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0

Layout : near=2

                    ^^^^^^

This layout is described at
http://en.wikipedia.org/wiki/Non-standard_RAID_levels#Linux_MD_RAID_10

Assuming the info there is correct, mirrored devices are [0,1] and [2,3]

Quoted 15 lines

Chunk Size : 64K

Name : of:0 (local to host of) UUID : 63b2145a:49030744:41b8f5b4:cb11bc1d
Events : 19

Number Major Minor RaidDevice State
0 8 17 0 active sync /dev/sdb1
1 8 33 1 active sync /dev/sdc1
2 8 49 2 active sync /dev/sdd1
3 8 65 3 active sync /dev/sde1
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Torbjørn Skagestad
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