For quite some time I have been using zfs send -R fsn...@snapname | dd
of=/dev/rmt/1ln to make a tape backup of my zfs file system. A few weeks back
the size of the file system grew to larger than would fit on a single DAT72
tape, and I once again searched for a simple solution to allow dumping of a zfs
file system to multiple tapes. Once again I was disappointed...
I expect there are plenty of other ways this could have been handled, but none
leapt out at me. I didn't want to pay large sums of cash for a commercial
backup product, and I didn't see that Amanda would be an easy thing to fit into
my existing scripts. In particular, (and I could well be reading this
incorrectly) it seems that the commercial products, Amanda, star, all are
dumping the zfs file system file by file (with or without ACLs). I found none
which would allow me to dump the file system and its snapshots, unless I used
zfs send to a scratch disk, and dumped to tape from there. But, of course,
that assumes I have a scratch disk large enough.
So, I have implemented zfsdump as a ksh script. The method is as follows:
1. Make a bunch of fifos.
2. Pipe the stream from zfs send to split, with split writing to the fifos (in
sequence).
3. Use dd to copy from the fifos to tape(s).
When the first tape is complete, zfsdump returns. One then calls it again,
specifying that the second tape is to be used, and so on.
>From the man page:
Example 1. Dump the @Tues snapshot of the tank filesystem
to the non-rewinding, non-compressing tape, with a 36GB
capacity:
zfsdump -z t...@tues -a "-R" -f /dev/rmt/1ln -s 36864 -t 0
For the second tape:
zfsdump -z t...@tues -a "-R" -f /dev/rmt/1ln -s 36864 -t 1
If you would like to try it out, download the package from:
http://www.quantmodels.co.uk/zfsdump/
I have packaged it up, so do the usual pkgadd stuff to install.
Please, though, [b]try this out with caution[/b]. Build a few test file
systems, and see that it works for you.
[b]It comes without warranty of any kind.[/b]
Tristram
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