To: "Paul Suhler" <Paul.Suhler@Quantum.Com> Cc: owner-t10@t10.org, t10@t10.org Subject: RE: Drive behavior issue when START STOP unit forces drive to idle power condition From: Kevin D Butt <kdbutt@us.ibm.com> Date: Fri, 30 May 2008 10:29:06 -0700 X-Message-Number: 8825 Formatted message: HTML-formatted message Also, don't forget any issues that might come out of Reservations. I don't know how start/stop unit interacts with reservations, but if you are counting starts and stops you probably need to take into account what happens with a PREEMPT type of reservation (if there is any interaction here). Also, issues that come out of the Media Changer community. Kevin D. Butt SCSI & Fibre Channel Architect, Tape Firmware MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744 Tel: 520-799-2869 / 520-799-5280 Fax: 520-799-2723 (T/L:321) Email address: kdbutt@us.ibm.com http://www-03.ibm.com/servers/storage/ "Paul Suhler" <Paul.Suhler@Quantum.Com> Sent by: owner-t10@t10.org 05/29/2008 04:50 PM To <t10@t10.org> cc Subject RE: Drive behavior issue when START STOP unit forces drive to idle power condition * From the T10 Reflector (t10@t10.org), posted by: * "Paul Suhler" <Paul.Suhler@Quantum.Com> * There's a potential issue with this, which the media changer community ran into with the PREVENT/ALLOW MEDIUM REMOVAL command. If one of the initiators issues a START UNIT and then dies, the count will never get back to zero. After the initiator recovers, it's unlikely that it will remember that it has an outstanding START and needs to issue a STOP. Cheers, Paul ___________________________________ Paul A. Suhler | Firmware Engineer | Quantum Corporation | Office: 949.856.7748 | paul.suhler@quantum.com ___________________________________ Disregard the Quantum Corporation confidentiality notice below. The information contained in this transmission is not confidential. Permission is hereby explicitly granted to disclose, copy, and further distribute to any individual(s) or organization(s), without restriction. -----Original Message----- From: owner-t10@t10.org [mailto:owner-t10@t10.org] On Behalf Of Rao, Santosh Ananth Sent: Thursday, May 29, 2008 3:59 PM To: Gerry.Houlder@seagate.com; t10@t10.org Subject: RE: Drive behavior issue when START STOP unit forces drive to idle power condition * From the T10 Reflector (t10@t10.org), posted by: * "Rao, Santosh Ananth" <santosh.rao@hp.com> * It would be worth exploring alternatives for the target device (either individual JBOD drives or array controllers) to track the number of START UNITs received from individual I-T-L nexi (or hosts per logical unit) and count down the corresponding STOP UNITs so that the drives corresponding to the logical unit can be spun down when the STOP UNIT count matches the START UNITs initially received. Being able to track host closure of all active references to a logical unit allows the target device to conserve power by spinning down the drive or set of drives mapping to that logical unit when the last application reference to the logical unit has been closed (volume group de-activated on the host, filesystem unmounted, database shutdown, etc). Thanks, Santosh Rao HP-UX Storage. > -----Original Message----- > From: owner-t10@t10.org [mailto:owner-t10@t10.org] On Behalf Of > Gerry.Houlder@seagate.com > Sent: Thursday, May 29, 2008 1:55 PM > To: t10@t10.org > Subject: Drive behavior issue when START STOP unit forces drive to > idle power condition > > * From the T10 Reflector (t10@t10.org), posted by: > * Gerry.Houlder@seagate.com > * > > While working on my additional idle power conditions proposal > (08-184) I encountered this issue with using START STOP UNIT command > to force the drive to idle mode. > > Situation: initiator sends START STOP UNIT command that forces drive > to idle power condition. As defined today, this action disables any > timers on the Power Condition Mode page (page 0x1A) that happen to be > enabled. Later a media access command causes the drive to transition > to active state to process the command. Since the timers are disabled, > the drive will stay in active state until another START STOP UNIT > command is sent. > > Problem: With multi-initiator systems, will all the initiators know to > send a START STOP UNIT command to put the drive back to idle to > conserve power? > If not, a drive that at least one initiator thinks is in an idle power > condition (conserving power) may actually be in active power condition > for long periods of time. > > Possible solution: change the START STOP UNIT command behavior so that > sending the command causes the drive to transition immediately to the > requested power condition but don't disable the timers. Then if the > drive goes to active power condition to process a media access > command, it will still go to idle power condition based on the > timers. This would at least limit the unnecessary active time of the > drive to the values set in the timers. > > I'd like to hear what other companies think of this situation. Will > drives always be fully manged in a multi-initiator system so the > stated problem will not be an issue or should something be changed to > limit the impact of this issue? Are there existing implementations > that use the current START STOP UNIT behavior? If not, perhaps we can > consider changing the behavior. > ----------------------------------------------------------- The information contained in this transmission may be confidential. Any disclosure, copying, or further distribution of confidential information is not permitted unless such privilege is explicitly granted in writing by Quantum Corporation. Furthermore, Quantum Corporation is not responsible for the proper and complete transmission of the substance of this communication or for any delay in its receipt. ------------------------------------------------------------ * * For T10 Reflector information, send a message with * 'info t10' (no quotes) in the message body to majordomo@t10.org