QErr, Basic Queuing and SBP-2

Charles Monia 237-6757 monia at AM.SHRMSG.SHR.mts.dec.com
Thu Feb 20 11:15:24 PST 1997

* From the SCSI Reflector (scsi at symbios.com), posted by:
* Charles Monia 237-6757 <monia at AM.SHRMSG.SHR.mts.dec.com>

I've discussed this with the OS developers here in Digital.  As I heard it, the
consensus regarding what we use and what we'd like to see is as follows:

Qerr = 00b (preserve pending tasks)  -- We use this now.  Should be mandatory
for **all** devices (including those only supporting basic queing model).

Qerr = 01b (clear task set on error)  -- Don't use now.  Not useful but should
retain for compatibility in devices that implement full queuing.

Qerr = 11b (clear selected tasks) -- Might use in the future.  Not needed if
Qerr=00b is required on Basic Queuing Devices.

So what we'd support is a change in the Basic Queuing Model to require that
Qerr = 00b be mandatory on such devices, with other flavors optional or
unsupported. If this is adopted, we have no preference regarding the Qerr=11b
variant.  If not, we'd be in favor of Ralph's proposal (it's the lesser of two

In sum, we feel that changing basic queuing to require Qerr= 00b behavior is
the best option.  Anything else requires a lot of effort for little or no gain.


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* Charles Monia, Storage Architecture Group                      *
* Digital Equipment Co.  Internet: charles.monia at shr.mts.dec.com *
* Tel: (508) 841-6757    X400: c=US; a=MCI; o=Digital; ou=SHR    *
* Fax: (508) 841-6100                                            *
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