Clarification on simple, incremental ZFS backup

Matthew Seaman matthew at
Wed Jul 1 16:03:19 UTC 2015

On 07/01/15 15:13, Brandon J. Wandersee wrote:
> There's a problem with this, though: when the filesystem is replicated
> all its properties are retained (naturally), including mountpoints. So
> the backup gets mounted over my local filesystem, making both
> useless. There's no way that I can see to unmount the backup filesystem
> (as that's now mounted to '/'), and importing the filesystem again after
> a reboot just mounts it over the local filesystem again. What am I doing
> wrong, here? Can anyone point me in the right direction? Does anyone
> here have a similar rsync-like backup scheme?

Yes, for *backup* using ZFS snapshots, you don't really want to use the
replication stream form of 'zfs send' -- just sending an incremental
update from a previous snapshot or bookmark means you can

    - save the data on your backup server to a different path
    - keep a lot more snapshots (ie. history) on your backup server
    - not have to keep the snapshots for old backups on the source

So long as the source and backup machines have a snapshot in common, or
even just a bookmark[*] on the source side corresponding to a snapshot
on the server side, then you're golden.  Oh, and incremental 'zfs send'
is *way* faster than rsync, especially when you've relatively few
changes to a large body of files.

I've some scripts I've been working on at work that they're happy for me
to publish, which I'll stick up on GitHub tonight.  Or else there's
zxfer in ports (which should have a website at,
but that doesn't seem to be working right now.)



[*] You need at least FreeBSD 10 for bookmarks as I recall.

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