Is it possible to replicate a ZFS or Btrfs raid volume in real-time (or as close to as possible, network specs aside) over a network?

ZFF and Btrfs are ideal because of their CoW properties.

I'm thinking something similar to DRBD, but DRBD won't work because it requires a single block device, and we're ruling out the option of exporting each disk as a DRBD device because that would get messy.

I don't want to use send/receive because they would be too slow, even if scripted.

Ideally, I'd like something relatively simple to avoid unnecessary complexity.


I'm not sure if this is exactly - or even close to - what you want but you can use DRBD on an iscsi-exported ZFS zvol. In fact, you don't even really need DRBD to do this, you could just export two zvols from two different ZFS servers using iscsi and make a linux mdadm raid device with them on the target system.

There's an add-on module for Google's ganeti VM management system to do this with DRBD and ZFS zvols at https://github.com/ffzg/ganeti-extstorage-zfs, which may provide a useful example of how to do this. Ganeti already does something similar with LVM and DRBD, so this just extends the capability to include ZFS.

btrfs doesn't have zvols or anything equivalent, so AFAIK it's not do-able with btrfs.

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