Re: Faster compression

Wayne Scott writes:

> From: "Michael 'Moose' Dinn" <dinn@xxxxxxxxxxxxxxxxxxxx>
>
> > Would people be interested in trying to get them to produce a PCI version?
> 
> Surely for the price of the card you could buy a bigger harddrive and
> then not use compression at all?
> 
> Or I suspect a faster processer would be pretty competive as well.  I
> really don't think that compression is a bottleneck for BackupPC.  And
> it would be really hard for a dedicated piece of hardware to be price
> competetive with commodity processors.

Agreed.  I doubt that hardware compression would improve BackupPC
performance by much.  Only new files (not already in the pool) need
to be compressed.  Existing files are uncompressed and compared.
Gzip uncompression is pretty fast (10x or so faster than compression).

If you look at the overall transfer speed reported for a full backup,
you might see numbers in the 0.5-2MB/s range.  If 90% of those files
are already in the pool, then only 10% of that data has to be compressed,
ie: 0.05-0.2 MB/sec compression rate.  If you benchmark gzip you should
find it will run a lot faster than that.  So even if gzip was instantaneous,
the overall performance won't improve measurably.

Craig


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