Re: [BackupPC-users] incremental backup always transferring whole directory?!

[kral <kr...@fr...>]

Les Mikesell a écrit :
> On Sat, 2006-06-03 at 09:39, Michael Helmling wrote:
> 
>>Hello,
>>I set up backuppc to back up my home directory (currently only this, I want to 
>>test the software).
>>
>>At first I did a full backup with tar, then switched over to rsync. Now every 
>>incremental backup he transfers the whole directory again (about 4 
>>Gigabytes), even though only a few megabytes change. Is this normal? Is it 
>>because the full backup was made with tar and not rsync?
>>I am searching for a backup solution for about 30 computers in a LAN, and if 
>>every time the whole stuff would be transferred, it'd be unuseable for me.
> 
> 
> I don't think that is supposed to happen even the first time
> but it should definitely stop if you force a full backup
> after the change. Rsync incrementasl will tranfer everything
> changed since the last full, though, so you'll want to do
> fulls fairly often.  30 machines shouldn't be a problem if
> the full runs don't all happen on the same night.
> 

The behavior you describe stick more with differential backups.
In Incrementals, saved files should refer to the last backup only.
The drawback
is that to restore the state Full +day3, you need:
Full + day1_Inc + day2_Inc + day3_Inc.

With Differentials, to restore the state Full +day3, you only need Full +
Day3_Diff (Day3_inc already include Day2_inc & Day1_inc)

Inc backup focus on backup speed, but is more slower on restores.
Diff backup focus on restore speed, but is less faster on backups.