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