In a message dated: Mon, 23 Aug 2004 15:12:52 EDT
Frederic Medery said:

>Thanks,
>in fact what I want is to speed up my backup so i moved my tape charger 
>to the biggest server, now I have a /amanda with 160 GB of free space. I 
>thought that HW compression would also speed up my backup.

I find that an illogical assumption.  If you have N clients all 
streaming data to a central host, which then has to stream that data 
to a tape drive, and the tape drive then has to compress that stream, 
then the compression becomes the bottleneck.  By using hw compression 
in that manner, you've inserted an additional hoop for the data to 
jump through before actually getting onto the tape.  Therefore, by 
definition, the whole process will be slowed down some (even if only 
by a negligible amount).

To actually speed up the backup process, it's probably better to 
perform client side compression, thereby distributing the process 
such that it is performed in parallel on the X clients you have.
This way, when the data, when it arrives at the server, is already in 
the form it's meant to be on tape; i.e. there's no longer a 
bottleneck at the tape drive.

Just my $.00002 :)
-- 
Seeya,
Paul

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