James Dickens wrote:
Why not make a snapshots on a production and then send incremental
backups over net? Especially with a lot of files it should be MUCH
faster than rsync.
because its a ZFS limited solution, if the source is not ZFS it won't
work, and i'm not sure how much faster incrementals would be than
rsysnc since rsync only shares checksums untill it finds a block that
has changed.
'zfs send' is *incredibly* faster than rsync.
rsync needs to traverse all the metadata, so it is fundamentally O(all
metadata). It needs to read every directory and stat every file, to
figure out what's been changed. Then it needs to read all of every
changed file to figure out what parts of it have been changed.
In contrast, 'zfs send' essentially only needs to read the changed data,
so it is O(changed data). We can do this by leveraging our knowledge of
the zfs internal structure, eg. block birth times.
That said, there is still a bunch of low-hanging performance fruit in
'zfs send', which I'll be working on over the next few months. And of
course if you need a cross-filesystem tool then 'zfs send' is not for
you. But give it a try if you can, and let us know how it works for you!
--matt
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