software raid queries

[Chiu, PCM (Peter)]

Dear all,

Having set up a software raid using the command:

mdadm --create /dev/md0 --level=5 --raid-devices=4 /dev/hda5 /dev/hdb5 /dev/hdc5 /dev/hdd5

I can make an ext3 file system okay.

If I then disable one drive using the command:

mdadm /dev/md0 -f /dev/hdd5 -r /dev/hdd5

I seem to have some trouble in re-enabling the drive again

using the command:

mdadm /dev/md0 -a /dev/hdd5

or

raidhotadd /dev/md0 /dev/hdd5

What is missing here to rebuild a degraded raid?

The doc http://unthought.net/Software-RAID.HOWTO/Software-RAID.HOWTO.txt suggests it is possible to grow a raid0/5 file system,

but I tried

mdadm /dev/md0 -a /dev/hdd6

mdadm /dev/md0 -G

resize2fs /dev/md0

they don't seem to do much to extend a raid 5 file system.

Any idea?

Many thanks.