[NTLUG:Discuss] Disk performance.

[Kevin Brannen]

Steve Baker wrote:
> 
> Jim Wildman wrote:
> >
> > For 100's of gigs, I would definitely look at scsi and maybe even an
> > external hardware raid cabinet.  This is not going to be cheap...
> 
> Tell me the bad news.
> 
> > Other issues to consider:
> 
> >         1) How many drives do you need on each controller?
> 
>              I may need up to 0.6 Terabytes in the largest system,
>              as little as 50Gb in the smallest.  So - between 1 and ~12
>              drives.  You can have 16 widgets on a SCSI bus - right?
> 

As has been pointed out, 7 on Narrow and 15 on wide; but you don't want to max
out a SCSI chain with high performance devices--or so I've always been told. 
On my SCSI-2 system, I try to keep it to 3 maybe 4 disks for the entire chain;
otherwise I may saturate the host adaptor (HA).  I think it would be a real
waste of money to pay top dollar for a good HA and fast HDs, then put more HD
throughput on the chain than the HA can handle. :-)

And this floats further up the line...what if you get one of the
UltraWide-SCSI-3 controllers that can do 160MB/s and you put enough drives on
it to almost saturate it, can your system bus handle that *along with
everything else it's doing*?

When you get into specialized systems like this, life becomes a balancing
act.  (Duh! :-)

Kevin