Deferred error handling with ACA

Gerry Houlder Gerry_Houlder at notes.seagate.com
Mon Sep 26 09:01:35 PDT 1994


Jeff William's reply to an earlier message:
 
>The discussion of deferred errors should not be mentioned with the autoclearing
>of ACA.  They are distinct items.  ACA does not change the manner in which the
>deferred errors are reported or cleared.  An ACA does not exist until the
>CHECK is returned to the initiator.  At that time, the ACA is treated as Bob's
>proposal states.  The deferred error handling of new I/O and old I/O is
>separate and should not be combined with ACA since the time domains are
>distinct.
>
I'm not so concerned about when the "deferred error" is reported, I am
concerned about what the drive should do in the time between the deferred error
occurs and it is able to report it. For example, an unrecovered write error
with write caching enabled. My programmers and customers have a strong
preference to not begin any new commands (excepting other write operations that
were merged with the command with the failure) until the deferred error is
reported. Does Bob's proposal suggest that previously queued commands from
other initiators can/should be executed during this time? Should new commands
|from other initiators be queued or even executed rather than completed with ACA
Active status? We would rather treat commands for other (non-failing)
initiators as if the ACA begins as soon as the error occured, not when it was
reported to the failing initiator (which could be a long time span). I think we
need to add some wording to specify how to handle this situation. Most
customers like the concept of "stop everything else until the error has been
reported", and existing ACA wording doesn't recommend this or (in some people's
opinion) may not even allow this.
--
Gerry Houlder -- Gerry_Houlder at notes.seagate.com
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### OGATE Version 8 message trace and attachment information:
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### Org Date:    09-26-94 06:54:55 AM
### From:        Gerry Houlder at SEAGATE
### To:          scsi @ WichitaKS.NCR.COM @ internet
### Subject:     Deferred error handling with ACA
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