Hi Folks,
I've inherited an old RH7 system that I'd like to upgrade to
CentOS6.1 by means of wiping it clean and doing a fresh install.
However, the system has a software raid setup that I wish to keep
untouched as it has data on that I must keep. Or at the very least, TRY
to keep. If all else fails, then so be it and I'll just recreate the
thing. I do plan on backing up the data first in case of disasters.
But I'm hoping I don't have to considering there's some 500GiB on
it.
The previous owner sent me a breakdown of how they build the raid
when it was first done. I've included an explanation below this message
with the various command outputs. Apparently their reason for doing it
the way they did was so they can easily add drives to the raid and grow
everything equally. It just seems a bit convoluted to me.
Here's my problem: I have no idea what the necessary steps are to
recreate it, as in, in what order. I presume it's pretty much the way
they explained it to me:
- create partitions
- use mdadm to create the various md volumes
- use pvcreate to create the various physical volumes
- use lvcreate to create the two logical volumes
If that's the case, great. However, can I perform a complete
system wipe, install CentOS 6.1, and re-attach the raid and mount the
logical volumes without much trouble?
What follows is the current setup, or at least, the way it was
originally configured. The system has 5 drives in it:
sda = main OS drive (80 GiB)
sdb, sdc, sdd, and sde: raid drives, 500 GiB each.
The setup for the raid as I've been explained was done something
like this:
First the four drives were each partitioned into 10 equal size
partitions. fdisk shows me this:
fdisk -l /dev/sdb
Disk /dev/sdb: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 1 6080 48837568+ 83 Linux
/dev/sdb2 6081 12160 48837600 83 Linux
/dev/sdb3 12161 18240 48837600 83 Linux
/dev/sdb4 18241 60801 341871232+ 5 Extended
/dev/sdb5 18241 24320 48837568+ 83 Linux
/dev/sdb6 24321 30400 48837568+ 83 Linux
/dev/sdb7 30401 36480 48837568+ 83 Linux
/dev/sdb8 36481 42560 48837568+ 83 Linux
/dev/sdb9 42561 48640 48837568+ 83 Linux
/dev/sdb10 48641 54720 48837568+ 83 Linux
/dev/sdb11 54721 60800 48837568+ 83 Linux
Then they took each partition on one drive and linked it with the
same partition on the other drive. So when I look at mdadm for each
/dev/md[0-9] device, I see this:
mdadm --detail /dev/md0
/dev/md0:
Version : 00.90.03
Creation Time : Wed Aug 29 07:01:34 2007
Raid Level : raid5
Array Size : 146512128 (139.72 GiB 150.03 GB)
Used Dev Size : 48837376 (46.57 GiB 50.01 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Tue Jan 17 13:49:49 2012
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 256K
UUID : 43d48349:b58e26df:bb06081a:68db4903
Events : 0.4
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
... and pvscan says:
pvscan
PV /dev/md0 VG VolGroup00 lvm2 [139.72 GB / 0 free]
PV /dev/md1 VG VolGroup00 lvm2 [139.72 GB / 0 free]
PV /dev/md2 VG VolGroup00 lvm2 [139.72 GB / 0 free]
PV /dev/md3 VG VolGroup00 lvm2 [139.72 GB / 0 free]
PV /dev/md4 VG VolGroup00 lvm2 [139.72 GB / 0 free]
PV /dev/md5 VG VolGroup00 lvm2 [139.72 GB / 0 free]
PV /dev/md6 VG VolGroup00 lvm2 [139.72 GB / 0 free]
PV /dev/md7 VG VolGroup00 lvm2 [139.72 GB / 0 free]
PV /dev/md8 VG VolGroup00 lvm2 [139.72 GB / 0 free]
PV /dev/md9 VG VolGroup00 lvm2 [139.72 GB / 139.72 GB free]
Total: 10 [1.36 TB] / in use: 10 [1.36 TB] / in no VG: 0 [0 ]
(evidently /dev/md9 isn't being used ... emergency spare?)
And from there, they created the logical volumes which lvscan says are:
lvscan
ACTIVE '/dev/VolGroup00/LogVol00' [1.09 TB] inherit
ACTIVE '/dev/VolGroup00/LogVol01' [139.72 GB] inherit