redhat mirrorin..

[ac325ci]

how do i break a mirror using mdadm ?

 

[Annihilannic]

To what end? Do you wish to have two copies of the data, or drop one of them permanently?

I tried it with two loopback devices just for fun...

[tt] # make some loopback devices
dd if=/dev/zero of=disk0 count=10240
dd if=/dev/zero of=disk1 count=10240
losetup /dev/loop0 /var/tmp/disk0
losetup /dev/loop1 /var/tmp/disk1
# create and mount the mirror
mdadm --create /dev/md0 -n 2 -l1 /dev/loop0 /dev/loop1
mke2fs /dev/md0
mkdir /mnt/md0
mount /dev/md0 /mnt/md0
cp a bunch of stuff /mnt/md0
# fail and then remove one of the devices
mdadm /dev/md0 -f /dev/loop1
mdadm -D /dev/md0
mdadm /dev/md0 -r /dev/loop1
mdadm -D /dev/md0
# mount the 'failed' device on a separate mountpoint
mkdir /mnt/loop1
mount /dev/loop1 /mnt/loop1[/tt]

Using that method I was effectively able to mount a snapshot of the original filesystem.

Annihilannic.

 

[ac325ci]

i'd like to keep two copies of the data while the mirror is broken.. if i do a failed of one i lose the data..

 

[Annihilannic]

No you don't. I didn't with the test above, why would you? when I mounted the so-called 'failed' loop1 device it had all of the original data on it. Surprisingly it didn't even need an fsck to mount it!

Annihilannic.