[CentOS] estimating backuppc

Wed Sep 17 05:22:40 UTC 2008
Les Mikesell <lesmikesell at gmail.com>

Craig White wrote:
> On Wed, 2008-09-17 at 16:42 +1200, Spiro Harvey wrote:
>>> If we add hard drive storage for backups instead of buying LTO-3 tape
>>> drive, how much storage would we want for backing up 2Tb of binary
>>> data...surely not 6 Terrabytes?
>> assuming that three week rotation is full backups only, then 2x3 is
>> indeed 6.
>> However, most people do incremental backups daily and fulls once a
>> week. If this the case, you will need more.
>> Your backups will probably be compressing the files, or rather,
>> archiving them into tarballs, cpioballs, or whatever. However, JPGs and
>> most movie formats will not compress well as they are already
>> compressed very heavily. So a full 2G backup will likely cost you 2G. 
>> There are a lot of factors involved and there is a lot more to setting
>> up a good backup regime than figuring out how much disk to throw at a
>> problem. Come the first disaster, they won't be your customer any more.
> ----
> I understand this and I normally use bacula and am not familiar with
> backuppc but I gather that guessing that 90% of the files will not
> change in any given week, it will probably require less but I have no
> experience with backuppc

Backuppc finds all identical files and replaces them with hardlinks to a 
single pooled and optionally compressed copy.  Unchanged content won't 
take additional space regardless of the number of backup runs you keep. 
However, even a small change will cause a complete separate copy to be 
stored, so the space you need will depend on what changes you have over 
the time you want to keep online.

   Les Mikesell
    lesmikesell at gmail.com