???---How to read from RAIDSETFAULTYed-RAIDHOTREMOVEd partition---???

[Dmitri Barsoukov]

Is it possible to use one of RAID1 mirrors for backup? I mean sync file
system, lock it, then remove one mirror, make back from it, then
raidhotadd it.

cat /etc/raidtab:
raiddev /dev/md0
raid-level 1
nr-raid-disks 2
chunk-size 32
persistent-superblock 1
device /dev/hda7
raid-disk 0
device /dev/hdb7

Then
sync;sync
raidsetfaulty /dev/md0 /dev/hdb7
raidhotremove /dev/md0 /dev/hdb7

So can I now activate /dev/hdb7, probably as degraded mirrir, make
backup from it and then return it back to md0 with

raidhotadd /dev/md0 /dev/hdb7

I know in solaris it's possible taking submirrir offline and then
brining it online back. But solaris and linux have different metadevices
structeres.

[Dmitri Barsoukov]

Well, replaying to myself...

Yes, if you don't have lvm on top md metadevices, you can mount offline
submirror as nomal partition.Having lvm make things more complicated.
The only way I found is:

-dettache submirror with raidsetfaulty, raidhotremove
-change partiotion type to (Linuv LVM) with fdisk
-make PV on thet partition with pvcreate
-add it to VG with vgextend
-make snapshot of LV in concern with lvcreate -s
-make backup of that snapshot LV
-remove this LV with lvremove
-partition it to 8e (Linux raid auto)
-bring it back to mirror with raidhotadd

Any comments wellcome