Thanks for that Jim!

Sounds like a plan there... One question about the storing ZFS dumps in a
file... So, the idea of storing the data in a SFTP server which has an
unknown underlying file system... Is that defiantly off limits, or can it
be done? and should i be doing a full dump or just an incremental one?
maybe incremental daily, and then a full dump weekly?



On Fri, Oct 5, 2012 at 9:36 AM, Jim Klimov <> wrote:

> 2012-10-05 11:17, Tiernan OToole wrote:
>> Also, as a follow up question, but slightly unrelated, when it comes to
>> the ZFS Send, i could use SSH to do the send, directly to the machine...
>> Or i could upload the compressed, and possibly encrypted dump to the
>> server... Which, for resume-ability and speed, would be suggested? And
>> if i where to go with an upload option, any suggestions on what i should
>> use?
> As for this, the answer depends on network bandwidth, reliability,
> and snapshot file size - ultimately, on the probability and retry
> cost of an error during transmission.
> Many posters on the list strongly object to using files as storage
> for snapshot streams, because in reliability this is (may be) worse
> than a single-disk pool and bitrot on it - a single-bit error in
> a snapshot file can render it and all newer snapshots invalid and
> un-importable.
> Still, given enough scratch space on the sending and receiving sides
> and a bad (slow, glitchy) network in-between, I did go with compressed
> files of zfs-send streams (perhaps making recursion myself and using
> smaller files of one snapshot each - YMMV). For compression on multiCPU
> senders I can strongly suggest "pigz --fast $filename" (I did have
> problems in pigz-1.7.1 compressing several files with one command,
> maybe that's fixed now). If you're tight on space/transfer size more
> than on CPU, you can try other parallel algos - pbzip2, p7zip, etc.
> Likewise, you can also pass the file into an encryptor of your choice.
> Then I can rsync these files to the receiving server, using "rsync -c"
> and/or md5sum, sha256sum, sha1sum or whatever tool(s) of your liking
> to validate that the files received match those sent - better safe
> than sorry. I'm usually using "rsync -cavPHK" for any work, which
> gives you retryable transfers in case network goes down, status bar,
> directory recursion and hardlink support among other things.
> NFS is also retryable if so configured (even if the receiver gets
> rebooted in the process), and if you, for example, already have
> VPN between two sites, you might find it faster than rsync which
> involves extra encryption - maybe redundant in VPN case.
> When the scratch area on the receiver has got and validated the
> compressed snapshot stream, I can gzcat it and pipe into zfs recv.
> This ultimately validates that the zfs-send stream arrived intact
> and is fully receivable, and only then I can delete the temporary
> files involved - or retry the send from different steps (it is
> possible that the initial file was corrupted in RAM, etc.)
> Note that such approach via files essentially disables zfs-send
> deduplication which may be available in protocol between two
> active zfs commands, but AFAIK this does not preclude you from
> receiving data into deduped datasets - local dedup happens upon
> block writes anyway, like compression, encryption and stuff like
> that.
> HTH,
> //Jim Klimov
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