On Sat, 28 Mar 2009 09:55:04 -0500
Ed Wilts <ewilts AT ewilts DOT org> wrote:

> On Sat, Mar 28, 2009 at 1:07 AM, Dean Allen <dean.deano AT gmail DOT com> 
> wrote:
> 
> > Before you get too far into design, you should work out how fast the
> > backups to disk actually are. This can have a big influence on how you
> > use your DSSU. I have a 3TB DSSU, (RAID 6 SATA) and I can't get any
> > better than about 50 MB/sec out of it (usually about 30 MB/sec). I can
> > get the tape drives up to 150 MB/sec. The majority of people seem to
> > think backing up to disk is going to be faster, but that's not
> > necessarily the case.
> 
> 
> I concur 100% - this has been our experience as well.
> 
> SATA drives are cheap, but they're slow.   You'll do about half the
> transactional rate of a good fibre channel or SCSI drive.
> 
> Many people think that because "it's just backups" that you can use cheaper
> SATA drives.  It's actually the opposite - backups are the highest I/O
> generator, by far, in many environments.

This really depends on the controller in use. There are controllers out there 
that will do 400MB/s or faster. We have 3ware and Areca controllers that do 
just this. This allows us to use multiple FULL gigabit connections in from 
clients as well as stage to multiple LTO3 tape drives at the same time using 
one media server.

--andy.
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