On Thu, Apr 2, 2015 at 4:25 AM, Alexander Rehbein
<alexander.rehbein AT fmex DOT de> wrote:
>>
>
> I've looked in the archive. Sometimes the incr backup is only 20mb,
> sometimes 200mb. Perhaps it is an better idea to only backup /var/vmail
> directory hourly instead of the full root path.
First, make sure you understand how backuppc works - and the type of
your mail files. If you use the old mbox mail format where messages
are appended to a single growing mailbox file, and use rsync, only the
difference will be transfered, but there is some CPU work involved to
compute the changes, and on the server side a complete new file copy
will be constructed and stored separately. Xfer methods other than
rsync will send the whole changed file. If your mail storage uses
one message per file like maildir format, rsync will only send the new
files (whether doing a full or incremental) and the ones where the
content matches the previous copy will all be pooled without taking
additional space. Non-rsync xfers will send only new files on
incrementals and everything on fulls, but existing content is still
found and pooled in storage. Note that 'new' means newer than the
previous full unless you have configured incremental levels.
So, there won't be much difference in the storage used regardless of
your mix of incremental/full runs. The main difference will be in
the time they take to complete and possibly the performance impact on
the target system. An incremental rsync run quickly skips fields
where the length/timestamp match the previous copy where the fulls do
a full read of the target content to do a block-checksum comparison,
Also, the fulls will rebuild the archive directory tree which may be
time-consuming with many small files, but that becomes the new base
for incrementals, making the next ones more efficient.
--
Les Mikesell
lesmikesell AT gmail DOT com
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