On Thu, Aug 31, 2017 at 11:51 AM, Gandalf Corvotempesta
<gandalf.corvotempe...@gmail.com> wrote:
> >
> Yes, now it's clear.
> But my issue is not bandwidth but time. A longer backup will increase
> load on the
> host for more time.
Yes, you need to pick your tradeoff between knowing your backup copy
is exactly correct and the amount of work the host does. But you'd
need to have a pretty good reason to change the default weekly full,
like your host not being able to function or a weekend not being long
enough to complete.
> So, a filled backup is only needed to prevent bit-rot or something
> similiar, right ?
> If my filesystem is ZFS, can I safely use a single filled backup for
> many months?
> There is no need to compare checksum in bpc, because ZFS already does this.
Some filesystems allow certain methods of writing that do not update
the directory timestamp. If you also don't change the length, an
rsync incremental won't read that file or back up the change. And
personally, I always liked the idea of regularly reading files to
detect hardware issues as early as possible.
>> "Filled" backups don't take a lot more space, just more time to build
>> the directory structure. If you are concerned about this, keep more
>> filled copies. In any case the next run will copy in anything
>> missing.
>
> Yes, on the run everyhting missing is synced. But what about a restore?
> If "file1" was created in the filled backup (now missing) and
> untouched in the subsequent incremental backup
> (thus it was not transferred), loosing the filled backup means to
> loose the "file1" ?
I don't really know the details of bpc4. I think it always fills the
most recent run and works backwards to clean up the old copies so you
should have whatever files are still there even if some were somehow
deleted. Still, if your pool filesystem is totally corrupted all
bets are off - like it would be with any system.
--
Les Mikesell
lesmikes...@gmail.com
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