I have a software RAID 10 array which I recently noticed went into a degraded state. The OS is CentOS 5.8.
It has 4x 500GB drives in 3 different arrays:
/dev/md0 is RAID 1 and mounted to /boot (200MB ext3)
/dev/md1 is RAID 10 and is swap (4GB swap)
/dev/md2 is RAID 10 and is the main system and data device (895GB ext3)
One of the drives has failed but only /dev/md2 (main system and data array) is degraded.
Here's the full mdadm and /proc/mdstat output... http://pastebin.com/VL0uYdU9
The problem seems to be failed sectors on one of the drives...
Dec 9 04:25:37 hostname smartd[3199]: Device: /dev/sdb, 1 Currently unreadable (pending) sectors
Dec 9 04:25:37 hostname smartd[3199]: Device: /dev/sdb, 1 Offline uncorrectable sectors
Replacing the drive ASAP is the ideal option. However I won't have physical access to the server for the next few weeks. I have backups going to another device on the network anyway so we should be covered if another drive goes (the mirror of the already failed drive).
Is there a way I can resize the file system of /dev/md2 down to under 500GB, so I can then migrate the degraded RAID 10 to a 3 drive RAID 1 array?
And can this be attempted online (full, verified, backups being made of course)?
I don't have access to the server for loading a recovery CD.
The linux software
RAID 10does not support any form of reshaping. Your only option to change it is, backup, to take it offline, build a new volume, and restore your data.