[Sunhelp] Dual-channel differential UltraSCSI card?

[James Lockwood]

On Wed, 23 Jun 1999, McMurry, James A. wrote:

> I want to get two controllers for the two drives.  If I add a third and
> fourth drive later, I'll have two drives on each controller.  It's best to
> limit tape drives to two per controller since they drag down the SCSI bus.
> You certainly don't want to put tape drives and hard disks on the same
> controller.  So goes the conventional thinking.

This is still true to a degree, but less so with modern tape drives with
good buffering.  Most modern drives do burst transfers at high speeds.

> Sun sells a "dual-channel differential UltraSCSI" PCI card.  I believe that
> this single card would give me what I want:  two discreet SCSI channels for
> each pair of drives.  It's not like I'll overload the card with the amount
> of data I'm transferring...
> 
> Is this correct?  Or should I be looking at a pair of single-channel cards?

The dual card should work fine, I've run several differential Exabyte
Mammoth libraries off of an E450 with this card with no problems.  If you
are a cheapskate (which, given the hardware you're connecting up, is
doubtful)  then some non-Sun Symbios dual-channel SCSI cards will work
(both the SE and differential dual-channel PCI cards are OEM Symbios).

-James