[Dirvish] replicate a vault with hardlinks

Richard Hector richard at walnut.gen.nz
Sun Oct 9 10:30:31 UTC 2016


On 09/10/16 21:11, Vortex wrote:
> On 09.10.2016 09:11, Richard Hector wrote:

>> My current plan is to write a script (which I've started) which will
>> copy the structure of the vault, possibly editing the config and other
>> administrative files, but merely hardlinking the contents of the
>> actual backup trees.
> 
> Just curious, but why a script if one cp -al and some manual config
> editing will do? :)

There's quite a lot of files that may need editing, if the per-backup
administrative files need it, and my backups go back 2 years ... but you
may be right. I may have got carried away :-)

>> Once I've done this, I hope I'll be able to continue backing up to
>> both vaults temporarily (just in case I stuff up the migration, and
>> have the old server writing to its maildir instead of relaying to the
>> new one), which will of course cause them to diverge.
> 
> Again, mind that you'll have only one set of data in the hard linked
> files. I don't know exactly how dirvish would handle this, but I see a
> risk in mixing different file contents from both servers into one hard
> linked file data in the backup. Only new files would be independent.

All changes result in new files. Dirvish doesn't ever edit existing
files; if the file has changed it writes a new one rather than linking
to the old.

I think I'm mostly answering my own questions ... except for figuring
out what config and housekeeping files need to change to match the vault
they're in - and how to make sure dirvish knows to use the existing
cloned backups as the basis for the first new one.

Richard




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