[T10] ZAC back pressure on ZBC

Joe Breher Joe.Breher at hgst.com
Mon Nov 16 14:51:54 PST 2015


Today’s ZAC call? What ZAC call? There is none listed on the T13 website. I have no record of receiving any such invitation. Who all was there? How did they know to attend?

That said, I think I understand the apparent conflict. However, it would seem possible to me that other commands in the queue may be (e.g.) RESET WRITE POINTER commands. As such, a subsequent OPEN ZONE command might indeed succeed. Perhaps unlikely, but a possibility.

Given the late stage of this game, it may be best to leave it as is.

Perhaps we should revisit the issue on Wednesday, at 1-3 Pacific, which is the time that T13 actually authorized a ZAC call.

Joe Breher
Storage Architecture Technologist
Standards Setting Organization
San Jose Research Center
HGST, a Western Digital company
(478) 2-Breher
(478) 227-3437

[cid:90D28901-5EA2-4283-92F9-2B1DD878731D at localdomain]

On Nov 16, 2015, at 3:10 PM, Ralph Weber <roweber at ieee.org<mailto:roweber at ieee.org>> wrote:

During today's ZAC call, the second to last paragraph in 5.5 (OPEN ZONE command) was discussed at length. The text in question is as follows.

"For a host managed zoned block device, if the ALL bit is set to one and the number of zones with a Zone Condition of EXPLICIT OPEN plus the number of zones with a Zone Condition of CLOSED is greater than the maximum number of open sequential write required zones, then the device server shall terminate the command with CHECK CONDITION status, with sense key set to ABORTED COMMAND and the additional sense code set to INSUFFICIENT ZONE RESOURCES."

Is simply retrying a OPEN ZONE (ALL) command likely to produce a successful result, which is what the ABORTED COMMAND sense key implies?

Absent changing some zones to EMPTY or FULL before retrying, the answer to the above question appears to be an emphatic **NO**.

As a result, several of those present on the call felt ILLEGAL REQUEST would be a better sense key than the one specified by ZAC and ZBC.

Notwithstanding the potential Houlderization that requesting a change to ILLEGAL REQUEST entails, those on the ZAC call agreed that ZAC would be best served by making the "adjustment" ... which means more work for the ZBC editor (if this stuff rolls downhill in the usual manner).

All the best,

.Ralph
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