Hi,
Rob Owens wrote on 2008-10-01 07:54:19 -0400 [Re: [BackupPC-users] Off-site
backup strategies]:
> > We have an on-site BackupPC server (2.1.2pl1) backing up 31 hosts, with
> > a total pool size of 1.8 TB.
> [...]
> > 1. Install BackupPC on the remote server, and do a full backup in the
> > office prior to deploying it to the colo. From then on, perform only
> > incremental backups.
> >
> This is what I do, except I do perform full backups (using rsync or
> rsyncd). It works well. Basically each machine on my lan gets backed
> up twice -- once locally and once remotely.
note that doing regular full backups with rsync(d) will usually *significantly
reduce* the amount of used bandwidth as has been explained multiple times.
> > 2. Use the remote server to hold a copy of the on-site BackupPC
> > server's file pool. The pool would be rsync'ed on-site initially and
> > then rsync'ed remotely from then on.
> >
> Against all advice on this list, I did this yesterday. I rsync'd my
> pool to a larger drive in the same machine. My pool size is 347G and
> it's been running for the past 15 hours or so. I've transfered 334G so
> far. My server has 3GB of RAM. It hasn't crashed, like many people
> thought it might, and it has only used 2MB of swap.
Some things to note:
1.) 1.8 TB is significantly more than 347G.
2.) It all depends on the number of files (and links to them), not on the
raw amount of data. You'll be fine with 1.8 TB of DVD images, 1.8 TB of
new spool won't work.
3.) Copied data is no progress indication. You may be 96% through or 1%. If
rsync happens to copy the cpool (or pool) directory first, you'll have
the bulk of the data in your copy, but without the pc directories it
is useless. That said, I would expect it to finish - given enough time -
because it should probably have crashed while constructing the file list
if it will at all (though I don't know how rsync stores the inode to file
name mapping - that could, in theory, be constructed on the fly, although
that seems unlikely).
4.) As always: if in doubt, try it out. Just don't depend on it working, it
may well turn out not to. Know what problems you are facing, so you won't
have to abort your attempt 90% through because you misjudged how long it
would take (though with rsync you can probably restart it later).
5.) Running rsync to produce an initial copy and running it later to keep the
copy up to date may have different characteristics. Test both before
depending on it working.
6.) Be prepared for running into problems by increasing file count over time.
Regards,
Holger
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