Linux Software Raid

Links

• A guide to mdadm
• mdstat
• How to use MDADM to manage software RAID disc arrays
• How To Manage RAID Arrays with mdadm
• RAID
• Software RAID Howto
• http://gentoo-wiki.com/HOWTO_Gentoo_Install_on_Software_RAID
• COMMON RAID DISK DATA FORMAT (DDF)
• Switching to mirroring
• http://www.sanitarium.net/golug/Linux_Software_RAID.html

• Remove a disk from soft raid
• Mdadm recovery and resync

HOWTO

Scan devices

mdadm --examine --scan --verbose /dev/sda2 /dev/sdb2 /dev/sdc2

Stop array

mdadm --stop /dev/md0

Re-add disk to array

mdadm /dev/md0 --re-add /dev/sdc1

List devices

Just

cat /proc/mdstat

What the howto and man mdadm don't tell

Checking the raid units

From man md:

echo check > /sys/block/md0/md/sync_action

check /proc/mdstat for status, and then set back to idle:

echo idle > /sys/block/md0/md/sync_action

Looking at your raid units

cat /proc/mdstat
mdadm --detail /dev/md0

(also shows what's going on when checking/resynching)

Hotswapping (scsi) disks

eject -s /dev/sda