[T13] ZAC & ZBC - reads to unwritten logical blocks / sectors

[Joe Breher]

Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1505281_f.htm">HTML-formatted message</a>

In yesterday's ZAC webex, the group collectively identified several holes in
the specification of behavior which include:
a) reads issued with Forced Unit Access;
b) reads issued to unmapped sectors; or
c) what is returned for PI,
for 'unwritten' sectors (i.e. not written since the last reset write pointer
operation to that zone) in:
a) sequential write preferred zones; or
b) sequential write required zones for which the URSWRZ bit (i.e. UR bit) is
set.
The participants on the call issued themselves action items to find out what
their organizations would prefer for these cases.
This email is to report HGST's collective wisdom on the matter. After some
internal discussion, we believe the most logical architectural choices are:
a) return 'initialization pattern' (as specified elsewhere - e.g. zbc-r03
4.3.3.1) for FUA reads;
b) return 'initialization pattern' for unmapped sector reads; and
c) return all F's for PI for sector reads,
for 'unwritten' sectors (i.e. not written since the last reset write pointer
operation to that zone) in:
a) sequential write preferred zones; or
b) sequential write required zones for which the URSWRZ bit (i.e. UR bit) is
set.
Thanks -
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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