Undestanding /proc/mdstat with raid10

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:
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
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Re: Undestanding /proc/mdstat with raid10

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On Tue, 2011-08-09 at 04:14 -0300, Sebastian Muniz wrote:
> 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]
>=20
> unused devices:
> Actually this is a Virtualbox machine with the same disk setup. I made 6=
=20
> x 100 Mbytes disks for the test.
>=20
> How can I tell which disks are mirrored?
That depends on the layout of your array. raid10 is not raid1+0
>=20
> My goal is to free the two mirror disks from md0, add two more free=20
> disks, create a new md1 raid5 array, and move the contents from md0 to md=
1
>=20
> Thanks in advance.
> Sebastian
>=20
> PS: in case it is relevant, i am adding the detailed md0 output.
>=20
> [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
>=20
> Update Time : Tue Aug 9 03:20:06 2011
> State : clean
> Active Devices : 4
> Working Devices : 4
> Failed Devices : 0
> Spare Devices : 0
>=20
> Layout : near=3D2
^^^^^^
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]

> Chunk Size : 64K
>=20
> Name : of:0 (local to host of)
> UUID : 63b2145a:49030744:41b8f5b4:cb11bc1d
> Events : 19
>=20
> 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
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html

--=20
Torbjørn Skagestad
Idé Til Produkt AS
torborn@itpas.no

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