[BackupPC-users] Linux backups with rsync vs tar

[charlesboyo <bac...@ba...>]

Hello list.

I have tried to relate with the various threads I have found regarding the issues with using the BackupPC/rsync combination; especially the 2007 thread with Les Mikesell and Timothy J. Massey.
More recently the question by Pavel Hofman and the response from Holger Parplies. But none of these have explained or resolved the problems I am facing.

I'm using BackupPC to take daily backups of a maildir totaling 250 GB with average file sizes of 500 MB (text mailboxes, these files change everyday).
Currently, my setup take full backups once a week and incremental backups every day between the full backups. The servers are directly connected with a cross-cable, allowing 100 Mbps.

However, these backups take about 8 hours to complete, averaging 8 Mbps and the BackupPC server is CPU-bound through-out the entire process. Thus I have reason to suspect the rsync overhead as being guilty.
Note that I have disabled hard links, implemented checksum caching, increased the block size to 512 KB and enable --whole-file to no avail.

With this background, I will appreciate answers to the following questions:

1. since over 90% of the files change every day and "incremental" backups involve transferring the whole file to the BackupPC server, won't it make better sense to just run a full backup everyday?
2. from Pavel's questions, he observed that BackupPC is unable to recover from interrupted tar transfer. Such interruptions simply cannot happen in my case. Should I switch to tar? And in the unlikely event that the transferred does get interrupted, what mechanisms do I need to implement to resume/recover from the failure?
3. What is the recommended process for switching from rsync to tar - since the format/attributes are reportedly incompatible? I would like to preserve existing compressed backups as much as possible.

Regards,

Charles 'Boyo

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