zbc theory of operation

Hannes Reinecke hare at suse.de
Tue Aug 5 05:51:11 PDT 2014

* From the T10 Reflector (t10 at t10.org), posted by:
* Hannes Reinecke <hare at suse.de>
Hi all,
I know ZBC is still far from being final, but nevertheless I've got 
some questions / issues which I've stumbled across recently.
The most crucial one is how to get the zone information for any 
given LBA. Typically one would use the REPORT ZONES command to 
retrieve the zone information for a given LBA.
However, zbc01 states that the REPORT ZONES will fail if the LBA is 
_not_ the starting LBA of a zone.
Which means we have to have an a-priory knowledge of the zone 
layout, ie we have to trawl through _all_ zone information before we 
can use REPORT ZONES with a non-zero LBA.
But if we have to slurp in _all_ zones before we can use the REPORT 
ZONES command in a meaningful manner it makes me wonder how it is 
supposed to be used.
Plus slurping in all zones upon startup takes up quite some time; 
I've measured several _minutes_ to retrieve the full zone information.
So how is the REPORT ZONES command to be used without a-priory 
knowledge of the zone layout?
Life would be _so much_ easier if we could lift the restriction on 
the REPORT ZONES command, so that it'll always return the zone 
information the LBA is contained in.
Dr. Hannes Reinecke		      zSeries & Storage
hare at suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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