Rotate backup drives with ZFS snapshot replication

[bernieTB]

Hi all,

I've done a fair bit of reading on this topic and can't really find a good (preferably definitive ;)) answer on my question...

Here it goes:

I have a number of datasets with following snapshots:
- Every 6 hours, keep 1 day
- Every 1 day, keep 1 month
- Every 1 month, keep 1 year

These snapshots are then replicated to my backup drives (each is 5 Tb).

My idea now is to:
- disable the replication task to 1 of the backup drives (keep the other one running)
- remove that backup drive and store off-site
- each month, rotate between the 2 backup drives (and re-enable the one task, disable the other)

Now, I read in a few posts that it may become impossible for the replication to catch up when I re-attach the drive I brought back onsite as some of the snapshots on that drive no longer exist on the FreeNas itself.

So, is this a good idea or not?

If not, what are the alternatives (but still keeping the rotation of the drives) - Rsync? Something else?

Thanks in advance!
Bernie

 

[bernieTB]

Anybody have any advice for me on this, please?

 

[Robert Trevellyan]

it may become impossible for the replication to catch up when I re-attach the drive I brought back onsite as some of the snapshots on that drive no longer exist on the FreeNas itself

As far as I understand the documentation for zfs send and zfs receive, whether this will be an issue depends on exactly how FreeNAS uses those commands under the hood. Some versions would require that both source and destination have at least one snapshot in common. In that case, you would still be able to do the replication by hand.

The problem with using rsync for this is that it doesn't have any concept of the ZFS filesystem structure, so nested datasets and their properties would not be preserved.