SUMMARY: Emulex or Adaptec SCSI-controller for SUN 3/60??

From: B|rje Josefsson (
Date: Mon Apr 29 1991 - 03:35:53 CDT


About one week ago I wrote:

>We are in progress of upgrading some of our 3/60's. Some of them have
>Adaptec (ACB4000) SCSI-controllers, and some of them have Emulex
>(MD21) controllers.

>The question is: Which (if any) of them is better - which machines
>should we keep. I have some feeling that the Emulex controller seems
>more reliable, but is that just a feeling, or??

I got several answers, and the general summary is that the machines
with the Emulex controllers is the ones to keep.

Thanks to all who replied.


Extract from (some of) the answers follows:

====> greg@cheers.Bungi.COM writes:

greg> The Emulex controller supports SCSI disconnect/reconnect whereas
greg> the Adaptec is actually more of a SASI controller and does
greg> not support that. Supporting disconnect/reconnect will greatly
greg> improve performance on a SCSI string containing more than one
greg> SCSI device. All tape drive interfaces should support disconnect/
greg> reconnect (ie, Emulex MT02, *not* the Sysgen board) or other
greg> devices will not be accessible until tapes are rewinding, etc.

greg> Also, the Emulex interfaces to ESDI drives which, while not as good
greg> as direct SCSI, are a lot faster than the ST-506 drives the Adaptec
greg> is interfacing to.

greg> Keep the ones with the Emulex controllers.

====> writes:

guyton> the adaptec 4000 "scsi" is translating scsi commands to/from st506 disks
guyton> the eumlex md21 "scsi" is translating scsi commands to/from esdi disks
guyton> and in general, esdi disks are new/faster/better than st506 disks
guyton> Also, I'd double check the "md21" disks, as they may actually be
guyton> native scsi disks (much better still). Sun OS uses the same software
guyton> for MD21 driven disks and for native scsi disks.

====> writes:

markm> The ACB4000 Adaptec is a SCSI/ST506 controller and the MD21 Emulex
markm> is a SCSI/ESDI controller. ST506 disks are slower and (generally)
markm> smaller than ESDI disks. The largest ST506 disk I've personally
markm> used is the XT2190 Maxtor, which formats to ~160Mb and has an
markm> average seek time of ~25ms. ESDI disks, on the other hand, can
markm> be as fast as 10-12ms avg seek time, and are available at least
markm> as large as 760Mb.

Borje Josefsson, Computer centre, University of Lulea, S-951 87 Lulea, Sweden
Tel: +46 920 91 262 (direct), +46 920 91 000 (operator). Fax: +46 920 912 45

Domain: Path: {uunet,mcsun,sunic}!!bj

This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:06:13 CDT