create a partial raid5

["stephan sperber" <quinte17@gmx.de>]

Hello!

Is it possible to create a Radi5 with only 2 disks? (I know that Raid5 
needs 3 to be really redundant)

With a Raid1 I can do things like:
mdadm -C /dev/md0 --force --raid-devices=1 /dev/hdb2
mkreiserfs /dev/md0

copy files from an older drive to the raid, get the old drive out and put 
the new disk for the raid in.
then
mdadm -G /dev/md0 --raid-disks=2
mdadm -a /dev/md0 /dev/hdc2

and the raid1 is now a real raid1 (after sync)

It would be great to have something similar for raid5:
mdadm -C /dev/md0 --force --raid-devices=2 /dev/hdb2 /dev/hdc2
mdadm -G /dev/md0 --raid-disks=3
mdadm -a /dev/md0 /dev/hda2

or
mdadm -C /dev/md0 --force --fail=/dev/hda2 --raid-devices=3 /dev/hdb2 /
dev/hdc2
mdadm -a /dev/md0 /dev/hda2

i know that this is possible with raidtools and /etc/raidtab.

is this possible with the recent version of mdadm or is it a planned 
feature (or not planned)?

thanks in advance
stephan



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