Hello!
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.
--Borje
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.
====> guyton@rand.org 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.
====> markm@apex.com 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: bj@dc.luth.se Path: {uunet,mcsun,sunic}!dc.luth.se!bj
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