Hello,
I am currently planning a migration of a one-machine setups to a
two-machine-cluster. Part of it will be migrating existing data to DRBD,
and I hope you can help me with this.
The current storage layout looks like this:
ext4 -> LVM -> LUKS/dm_crypt -> mdadm raid -> sda2/sdb2
That is, we have a software raid (level 5), which is encrypted using
LUKS. The encrypted device is PV for the LVM, which has one VG and
multiple ext4 formatted LVs.
I'd like to add DRBD like this:
ext4 -> LVM -> LUKS/dm_crypt -> DRBD -> mdadm raid -> sda2/sdb2
My primary goal is to let only one machine do the encryption (which will
be a new machine with AESNI) and then have DRDB distribute that
encrypted data to two machines.
Is this possible, and how would I go about migrating the existing setup
without losing any data? As I understand it, you would have to create a
DRBD device with /dev/md0 as lower-level device on each machine. Then
you would have to change the LUKS setup to open /dev/drbd0 as encrypted
device; from then on the LVM layer should see no difference, since it is
still using /dev/mapper/<crypted_volume> as PV, right?
What about metadata in this setup? Where would/could DRBD store it in
this case? Do some of DRBDs features like checksum-based replication
make sense in such a setup?
Thanks for your help,
Andreas
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