I introduced a bug in 15-113

Joe Breher Joe.Breher at hgst.com
Fri Jun 5 13:07:42 PDT 2015


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Hi Ralph -
I hate to be disagreeable, but I disagree with your disagreement.
The page 9 comment I wish to retract is not in 4.3.3.op.6.3, but in
4.3.3.op.6.2  Select a sequential write preferred zone, where I commented
"All zone management operations to sequential write preferred zones return
successful completion."
There is a very real limit on the number of concurrent explicitly open
sequential write preferred zones a device is able to support - for at least
some implementations. If this limit is reached, and there are no implicitly
open sequential write preferred zones, the device must fail the zone
management operation, as the guiding directive is that zone management
operations shall not cause explicitly open zones to be closed. Note the (y >
0) term in the expression.
I realize (now) that we currently have no mechanism to report such a limit.
This may be the root issue with this feature. We are still confabbing
internally with the proper resolution of this -- which is why I have not yet
forwarded proposed text -- but at least one solution is immediately apparent.
Unfortunately, it introduces a new technical requirement at a late date. This
would be to introduce a new VPD parameter of MAXIMUM NUMBER OF EXPLICITLY
OPEN SEQUENTIAL WRITE PREFERRED ZONES, and have a secondary test in the
'Select a sequential write preferred zone' path.
Suggestions for a less intrusive resolution are welcome.
Joe Breher
Storage Architecture Technologist
Standards Setting Organization
San Jose Research Center
HGST, a Western Digital company
(478) 2-Breher
(478) 227-3437
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On Jun 4, 2015, at 6:59 PM, Ralph Weber
<Ralph.Weber at wdc.com> wrote:
Joe,
I disagree with your retraction of the page 9 comment.
The only way an error is returned is if the second equation in 4.3.3.op.6.3
Select a sequential write required zone evaluates to true. If the values in
the equation are spelled out, the following must evaluate to true:
the number of sequential write required zones with a Zone Condition of
EXPLICITLY OPENED
ge
the contents of the MAXIMUM NUMBER OF OPEN SEQUENTIAL WRITE REQUIRED ZONES
field of the Zoned Block Device Characteristics VPD page
Now, if there is so much as one sequential write preferred zone open, then
the zoned device is not allowed to support any sequential write required
zones. Therefore, the number of sequential write required zoned with a Zone
Condition of EXPLICITLY OPENED must be zero.
Surely, zero should be a small enough number to be less than any valid
contents of the MAXIMUM NUMBER OF OPEN SEQUENTIAL WRITE REQUIRED ZONES field,
n'es pas?
All the best,
.Ralph
________________________________
From: Joe Breher [Joe.Breher at hgst.com]
Sent: Wednesday, June 03, 2015 10:45 AM
To: Ralph Weber; T10 org
Cc: Gerry Houlder
Subject: ZBC: I introduced a bug in 15-113
I just realized that I introduced a bug in 15-113r4 as modified.
On page 9, I commented "All zone management operations to sequential write
preferred zones return successful completion".However, in the case where
there are no implicitly opened zones available to be closed (i.e., all open
zones are explicitly opened zones), the zone management operation will indeed
return a non-successful completion.
I will have suggested text to correct this later today.
Joe Breher
Storage Architecture Technologist
Standards Setting Organization
San Jose Research Center
HGST, a Western Digital company
(478) 2-Breher
(478) 227-3437
This e-mail may contain confidential or legally privileged information of
HGST. If you are not the intended recipient, please notify us immediately by
responding to this e-mail and then deleting it from your system.



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