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Re: [BackupPC-users] Any procedure for using 2 external harddrives
2012-10-25 11:45:27
"Tyler J. Wagner" <tyler AT tolaris DOT com>
wrote on 10/25/2012 09:14:47 AM:
> On 2012-10-25 14:10, Bowie Bailey wrote:
> > On 10/24/2012 12:41 PM, dixieadmin wrote:
> >> I am currently using BackupPC 3.2.1 on SME Server 8.0. I
wanted
> to know if there is a correct procedure for using 2 different
> external harddrives as a backup source and to interchange them weekly?
> >
> > "interchange them weekly" ... Are you referring to
having a 2-drive
> > mirror and replacing one weekly? Or having one drive connected
at a
> > time and swapping them out weekly? Or having both drives
connected and
> > swapping both out for 2 different drives weekly?
>
> Because of the pool model that BackupPC uses for storage, there are
only
> two useful methods for using two different external drives:
>
> 1. Use RAID and remove one member periodically, to take offsite. This
is
> best done with 3 drives, actually.
>
> 2. Use the external drives as a target for ArchiveHost, and dump occasional
> tarballs of each host to them. This is OK for emergency restore but
won't
> give you a working BackupPC server if you want that.
Also, keep in mind that the original question shows
a fundamental lack of understanding in the way BackupPC works. BackupPC
is *NOT* a simple replacement for a tape drive. Swapping the entire
pool weekly will undermine the way BackupPC works: it's not designed
for that. And using preconceived ideas of traditional backup to shape
the way BacukpPC works is not a path that leads to success.
For BackupPC to work effectively, the pool stays in
place permanently, 100% of the time. You do not "interchange"
anything inside of BackupPC at all, with any frequency. Of course,
off-site backups are important, even essential. This is *NOT* achieved
by swapping pools. It's achieved by one of three ways:
1) Constantly mirroring the pool and occasionally
breaking the mirror to take it off-site. (Option 1 above). A
variation of this would be to take the pool down and make a copy of it,
then bring it back up (or use LVM snapshots to reduce the downtime). This
variation is left as an exercise for the reader: there are a *lot*
of unexpected details in that answer: problems with file-level copy
will most likely require block-level copies, LVM snapshots present performance
and reliability issues, etc.
2) Exporting a single copy of a specific backup to
a removable destination and moving that off-site. (Option 2 above).
A variation of this would be to make the destination for the archive
a remote filesystem already off-site, and there is no physical movement
at all.
There is a third option that was not mentioned:
3) Have two BackupPC systems that *both* back up the
same hosts in parallel. A variation of this would have the BackupPC
servers in different physical locations. This variation just about
requires the use of rsync, and even then is not always practical (if the
data changes per day/week/whatever are too vast, the bandwidth between
them too limited, or there is simply too much data to be able to back it
all up twice in a reasonable amount of time).
Tim Massey
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