Hi All.
I have a server which uses RAID10 made of 4 partitions for / and boots from
it. It looks like so:
mdadm -D /dev/md1
/dev/md1:
Version : 00.90
Creation Time : Mon Apr 27 09:25:05 2009
Raid Level : raid10
Array Size : 973827968 (928.71 GiB 997.20 GB)
Used Dev Size : 486913984 (464.36 GiB 498.60 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 1
Persistence : Superblock is persistent
Update Time : Mon Apr 7 21:26:29 2014
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : near=2, far=1
Chunk Size : 64K
UUID : 1403e5aa:3152b3f8:086582aa:c95c4fc7
Events : 0.38695092
Number Major Minor RaidDevice State
0 8 6 0 active sync /dev/sda6
1 8 22 1 active sync /dev/sdb6
2 8 54 2 active sync /dev/sdd6
3 8 38 3 active sync /dev/sdc6
As far as I know raid10 is ~ "a raid0 built on top of two raid1" (
http://en.wikipedia.org/wiki/Nested_RAID_levels#RAID_1.2B0 - raid10). So I
think that by default in my case:
/dev/sda6 and /dev/sdb6 form the first "raid1"
/dev/sdd6 and /dev/sdc6 form the second "raid1"
So is it so that if I fail/remove for example:
- /dev/sdb6 and /dev/sdc6 (different "raid1's") - the raid10 will be
usable/data will be ok?
- /dev/sda6 and /dev/sdb6 (the same "raid1") - the raid10 will be not
usable/data will be lost?
I read in context of raid10 about replicas of data (2 by default) and the
data layout (near/far/offset). I see in the output of mdadm -D the line
"Layout : near=2, far=1" and am not sure which layout is exactly used and
how it influences data layout/distribution in my case :|
I would really appreciate a definite answer which partitions I can remove
and which I cannot remove at the same time because I need to perform some
disk maintenance tasks on this raid10 array. Thanks for all help!
BR,
Rafal.
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