On 01/11/17 09:51, Dave wrote:
As already said by Romain Mamedov, rsync is viable alternative to
send-receive with much less hassle. According to some reports it can even be
faster.
Thanks for confirming. I must have missed those reports. I had never
considered this idea until now -- but I like it.
Are there any blogs or wikis where people have done something similar
to what we are discussing here?
I don't know any. Probably someone needs to write it.
We will delete most snapshots on the live volume, but retain many (or
all) snapshots on the backup block device. Is that a good strategy,
given my goals?
Depending on the way you use it, retaining even a dozen snapshots on a live
volume might hurt performance (for high-performance databases) or be
completely transparent (for user folders). You may want to experiment with
this number.
We do experience severe performance problems now, especially with
Firefox. Part of my experiment is to reduce the number of snapshots on
the live volumes, hence this question.
Just for statistics, how many snapshots do you have and how often do you
take them? It's on SSD, right?
Thanks. I hope you do find time to publish it. (And what do you mean
by portable?) For now, Snapper has a cleanup algorithm that we can
use. At least one of the tools listed here has a thinout algorithm
too: https://btrfs.wiki.kernel.org/index.php/Incremental_Backup
It is currently a small part of yet another home-grown backup tool which
is itself fairly big and tuned to particular environment. I thought many
times that it would be very nice to have thinning tool separately and
with no unnecessary dependencies, but...
BTW beware of deleting too many snapshots at once with any tool. Delete
few and let filesystem stabilize before proceeding.
Should I consider a dedup tool like one of these?
Certainly NOT for snapshot-based backups: it is already deduplicated almost
as much as possible, dedup tools can only make it *less* deduplicated.
The question is whether to use a dedup tool on the live volume which
has a few snapshots. Even with the new strategy (based on rsync), the
live volume may sometimes have two snapshots (pre- and post- pacman
upgrades).
For deduplication tool to be useful you ought to have some duplicate
data on your live volume. Do you have any (e.g. many LXC containers with
the same distribution)?
Also still wondering about these options: no-holes, skinny metadata,
or extended inode refs?
I don't know anything about any of these, sorry.
P.S. I still think you need some off-system backup solution too, either
rsync+snapshot-based over ssh or e.g. Burp (shameless advertising:
http://burp.grke.org/ ).
--
With Best Regards,
Marat Khalili
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