[BUGS] Any FreeBSD-11-stable ZFS experts on the list?

[Andrew Reilly]

Hi all,

I've been sending zfs snapshots to a zfs backup drive on my home server for years, now.  The scripts purr along, for the most part, and every so often (annually-ish) I replace the external backup drive and start again.  Those external drives don't have much of a lifespan, in my experience.

Anyway, somewhere in the last year, "something happened", and now I can't find my backup snapshots.  Any help or suggestions would be gratefully appreciated!

For example, I take nightly snapshots of tank/home to tank/home at 1 (after renaming previous night's snapshots and deleting the oldest), and then send tank/home at 1 to backup16/home at 1 after similarly renaming previous history of snapshots and deleting the oldest.  This shows all the appearance of working fine: the nightly backup logs show about the right amount of traffic and no execution errors.

I have been operating with snapdir=hidden, ever since I discovered that the various periodic scripts were timing out because they were trawling all of the .zfs/snapshot trees...  However, I've set snapdir=visible backup16/home and the .zfs directory is not showing up.  Indeed, there is nothing showing up in the directory at all.  And yet zfs list -t snapshot shows:

[... onwards to backup16/home at 90 ...]
backup16/home at 15    347M      -  2.00T  -
backup16/home at 14    347M      -  2.00T  -
backup16/home at 13    347M      -  2.00T  -
backup16/home at 12    346M      -  2.00T  -
backup16/home at 11    346M      -  2.00T  -
backup16/home at 10    347M      -  2.00T  -
backup16/home at 9     347M      -  2.00T  -
backup16/home at 8     348M      -  2.00T  -
backup16/home at 7     347M      -  2.00T  -
backup16/home at 6     347M      -  2.00T  -
backup16/home at 5     347M      -  2.00T  -
backup16/home at 4     347M      -  2.00T  -
backup16/home at 3     347M      -  2.00T  -
backup16/home at 2     355M      -  2.00T  -
backup16/home at 1        0      -  2.00T  -
[... onwards to other snapshots...]

/backup16/.zfs/snapshot does show up when I set snapdir=visible backup16, but it doesn't have anything in it, which I don't find surprising because I don't send any snapshots to it.  /tank/*/.zfs/snapshot all show up as expected, when I turn on snapdir=visible.  The only ones missing are the ones that I actually care about...

Now I admit that backup16/home at 1 having a size of zero looks suspicious.  I don't know why that would be happening.  Wasn't the case before, I'm sure.

This all *used* to work, and I've retrieved things from the backups in years gone past.

I'd be happy to post my backup script(s) if anyone cares to have a look.

Cheers,

Andrew Reilly
areilly at bigpond.net.au