persistent_reserve question

Gerry_Houlder at notes.seagate.com Gerry_Houlder at notes.seagate.com
Thu Feb 24 09:40:48 PST 2000


* From the T10 Reflector (t10 at t10.org), posted by:
* Gerry_Houlder at notes.seagate.com
*
My answers are inserted after your questions:





"peter" <dmonger at msn.com> on 02/23/2000 09:32:04 PM

To:   t10 at t10.org
cc:    (bcc: Gerry Houlder)

Subject:  persistent_reserve question



* From the T10 Reflector (t10 at t10.org), posted by:
* "peter" <dmonger at msn.com>
*
i was hoping to play around with persistent reservations this week but
unfortunately none of the disks in my office support it.  So i'm forced to
ask others for information - hopefully this is the right forum.

i have three questions.

1) can multiple initiators register using the same key?  If so does a
reservation using that key apply to all initiators?

ANS: Yes, multiple initiators can register with the same key. All "registrants
only" reservations apply to all registered initiators regardless of the value of
the key. Exclusive reservations still only apply to the original initiator even
if other iniitators register with the same key.

2) If initiator A has a reservation for shared access and init. B (who has
no reservation) tries to do a read/write will B get a reservation conflict?

ANS: When you say shared, I presume you mean "registrant only" type. If B is not
registered, it will get conflict status. If it is registered, it will get the
same access allowed to all other registered initiators. Refer to Annex B of
SPC-2 draft document for an exhaustive list of the possibilities.

3) is persistent reserve widely implemented?  base on my non-scientific
survey of 5 disks (3 FC, 2 scsi) i'd say no.

ANS: In general, only drives designed within the last year support the feature.
Fibre Channel interface tends to treat persistent reservations as "required"
while parallel SCSI has them as optional.

thanks,
-p

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