Mike, We use PAV for volumes containing CMS minidisks. We turned it on a few months ago on a system that we acquired with our last merger, and the user was quite pleased. It took a couple of hours off of their nightly batch. PAV is also on for volumes that contain SFS minidisks. It doesn't help for volumes that have SFS data minidisks (storage group 2+), because those are full packs, but it doesn't seem to hurt anything. Our catalog and log disks are a couple hundred cylinders each, and there are other CMS minidisks on those volumes. I presume we're getting some benefit there.
Dennis "Christmas dawned clear and cold; lovely weather for killing Germans, although the thought seemed somewhat at variance with the spirit of the day." -- War as I knew it, by Gen. George S. Patton, Jr. -----Original Message----- From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Mike Walter Sent: Monday, December 20, 2010 08:33 To: IBMVM@LISTSERV.UARK.EDU Subject: [IBMVM] General CMS minidisks and SFS on PAV DASD? We've always avoided using PAV volumes for general user (non-fullpack) CMS minidisks. Instead we've only used DASD defined as 3390-3 so that I/O queueing is minimized. That choice was in part due to management decisions. Over the past weekend we needed to move some z/VM DASD quickly -- and the target DASD was already defined as PAV DASD. The z/VM CP Planning and Administration manual clearly states that "z/VM Paging and SPOOLing operations do not take advantage of PAV." (no argument here). We'll still plan to keep page and SPOOL volumes on non-PAV 3390-3 DASD. But the same manual also states that "When multiple CMS volumes are defined on a real PAV volume, I/O operations by CMS can be concurrently scheduled on any real PAV base or alias subchannel by z/VM. The CMS user does not need to take any action for this to occur." Well, that's "book larn'in". Can anyone provide real-life results of using PAV volumes for general-purpose CMS user minidisks, and... for SFS filespaces? Do you see real I/O improvement for those apps? If so, the next time we're asked we might recommend larger 3390 volumes, mod 9's or 27's (depending on the number of available paths) to permit larger minidisks without SFS overhead, and improved SFS performance. Thanks! Mike Walter Aon Corporation The opinions expressed herein are mine alone, not my employer's. The information contained in this e-mail and any accompanying documents may contain information that is confidential or otherwise protected from disclosure. If you are not the intended recipient of this message, or if this message has been addressed to you in error, please immediately alert the sender by reply e-mail and then delete this message, including any attachments. Any dissemination, distribution or other use of the contents of this message by anyone other than the intended recipient is strictly prohibited. All messages sent to and from this e-mail address may be monitored as permitted by applicable law and regulations to ensure compliance with our internal policies and to protect our business. E-mails are not secure and cannot be guaranteed to be error free as they can be intercepted, amended, lost or destroyed, or contain viruses. You are deemed to have accepted these risks if you communicate with us by e-mail. ---------------------------------------------------------------------- This message w/attachments (message) is intended solely for the use of the intended recipient(s) and may contain information that is privileged, confidential or proprietary. If you are not an intended recipient, please notify the sender, and then please delete and destroy all copies and attachments, and be advised that any review or dissemination of, or the taking of any action in reliance on, the information contained in or attached to this message is prohibited. Unless specifically indicated, this message is not an offer to sell or a solicitation of any investment products or other financial product or service, an official confirmation of any transaction, or an official statement of Sender. Subject to applicable law, Sender may intercept, monitor, review and retain e-communications (EC) traveling through its networks/systems and may produce any such EC to regulators, law enforcement, in litigation and as required by law. The laws of the country of each sender/recipient may impact the handling of EC, and EC may be archived, supervised and produced in countries other than the country in which you are located. This message cannot be guaranteed to be secure or free of errors or viruses. References to "Sender" are references to any subsidiary of Bank of America Corporation. Securities and Insurance Products: * Are Not FDIC Insured * Are Not Bank Guaranteed * May Lose Value * Are Not a Bank Deposit * Are Not a Condition to Any Banking Service or Activity * Are Not Insured by Any Federal Government Agency. Attachments that are part of this EC may have additional important disclosures and disclaimers, which you should read. This message is subject to terms available at the following link: http://www.bankofamerica.com/emaildisclaimer. By messaging with Sender you consent to the foregoing.