Re: SCSI Hard Drive Questions
> Hi all,
>
> I'm considering purchasing a SCSI Hard Drive to hold my system on,
> and I was wondering about debian/kernel support for the Adaptec AHA-2940
> UW vs. the Adaptec AHA-2940 U2W. Also, is it economical to pay the extra
> $150 for an Ultra2 Wide controller and drive vs. an Ultra Wide? Will I
> see a justifyable return on the doubled speed? Sorry this is a bit
> off-topic, but I don't want to make a foolish choice...
The ultra2 wide provides twice as fast transfers to/from disk
as the ultra wide.
That won't help you *at all* if you connect a single scsi disk
only, because no single disk can sustain these high transfer
rates.
Several scsi disks (RAID or non-RAID) can saturate the 40MB/s
of ultra-wide, ultra2 will help you in this case.
So, the big questions are:
1) Are you going to hook up so many disks that needing over 40 MB/s
is possible at all? The sustained transfer speed of disks are
usually available from the manufacturer, or you can run big
tests. Don't confuse the sustainable rate with the
marketed burst transfer rate (which is 80 for any ultra2 drive)
3 drives that does 12MB/s won't be able to take advantage of ultra2,
and few drives are that fast.
2) Even if your system is capable of more than 40MB/s, will
you ever need that for *your* use of the machine?
Are you waiting for less-than 40MB/s disks for
long periods of time? Are the disks very busy for
long stretches of time? You *may* find the ultra2
useful if you can answer yes.
I wouldn't consider ultra2 (or even wide or ultra) for
a typical home machine. Not because home-user programs
are "fast enough as is", but because they simply can't
put enough load on the drives.
Helge Hafting
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