Ok, thanks a lot for this information.
It's very interessting.
Regards,
Romain
John Pettitt <[EMAIL PROTECTED]>
Envoyé par : [EMAIL PROTECTED]
05/12/2007 09:06
A
Rich Rauenzahn <[EMAIL PROTECTED]>
cc
"backuppc-users@lists.sourceforge.net"
<backuppc-users@lists.sourceforge.net>
Objet
Re: [BackupPC-users] Compression level
Craig Barratt wrote:
> Rich writes:
>
>
>> I don't think BackupPC will update the pool with the smaller file even
>> though it knows the source was identical, and some tests I just did
>> backing up /tmp seem to agree. Once compressed and copied into the
>> pool, the file is not updated with future higher compressed copies.
>> Does anyone know something otherwise?
>>
>
> You're right.
>
> Each file in the pool is only compressed once, at the current
> compression level. Matching pool files is done by comparing
> uncompressed file contents, not compressed files.
>
> It's done this way because compression is typically a lot more
> expensive than uncompressing. Changing the compression level
> will only apply to new additions to the pool.
>
> To benchmark compression ratios you could remove all the files
> in the pool between runs, but of course you should only do that
> on a test setup, not a production installation.
>
> Craig
>
The other point to keep in mind is that unless you actually need
compression for disk space reasons leaving it off will often be faster
on a CPU bound server. Since there is a script provided
(BackupPC_compressPool) to compress it later you can safely leave
compression off until you need the disk space.
John
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