Mark, > Yes, we're paging. A lot! And the page volumes are filling up too! Not being a performance geek, and without any knowledge of your environment other except that you have Linux for System z guests, something sounds a little fishy.
Just guessing from other's past posts: could it be that your Linux guests had been given VM sizes based on what the distributed servers had? IIRC, Linux caches a lot of files in its storage. That's great in a distributed server that has lower I/O throughput (all I/O is serviced by the CPU on the motherboard vs. being handed off to an I/O processor on System z), and where distributed memory is a lot cheaper than System z memory. On System z, memory is (relatively) expensive, I/O's are VERY fast (and do not impact the CPU much), and MDISK cache is quite good. Giving Linux for System z servers lots of memory because that's what they had on distributed servers (presuming that the memory is mostly file caching), and having the Linux server also cached in minidisk cache is quite a waste (double caching). IIRC, MDCACHE beats Linux cache in almost every case. If you have a good performance monitor for your Linux guests, try to see *why* they need so much memory. If it's file cache, try reducing the vm size significantly (IIRC, Jim Vincent used to recommend 2G or less for Websphere servers). Getting the Linux guest memory requirements reduced could improve your z/VM paging requirements. Good hunting! Mike Walter Hewitt Associates The opinions expressed herein are mine alone, not my employer's. "Mark Wheeler" <[email protected]> Sent by: "The IBM z/VM Operating System" <[email protected]> 02/23/2010 11:01 AM Please respond to "The IBM z/VM Operating System" <[email protected]> To [email protected] cc Subject Re: Adding different sized page volumes Yes, we're paging. A lot! And the page volumes are filling up too! Some new 3390-27 page volumes have been added, with all 32K cyls allocated to PAGE, and when the 3390-9's fill up, the mod27's do go beyond the 10016 cyl mark. I suspect (we haven't gotten this far yet) that when the mod 9's completely fill up, not only will block paging suffer (more), but most of the page-outs will be concentrated on the relatively few mod 27s. Gaackkk! I'm just trying to reconcile the admonishment not to mix page volume sizes with what people do in the real world. Since my options don't provide for the *ideal* solution, my preference is to adopt one that will provide the maximum benefit with the smallest downside. Best regards, Mark Date: Tue, 23 Feb 2010 08:37:06 -0800 From: [email protected] Subject: Re: Adding different sized page volumes To: [email protected] My experience was that the paging will be spread evenly until the -9s start filling up and then the additional space in the -27s will be used. That was from a recent experience with a combination of -3s and -9s. I have since converted everything to -9s. The only possible answer to the other question is, "It depends." If your system is not paging to DASD very much, it probably doesn't matter. If you are paging to DASD, then the lower the space utilization, the more likely that the system can realize the benefits of block paging. Regards, Richard Schuh From: The IBM z/VM Operating System [mailto:[email protected]] On Behalf Of Mark Wheeler Sent: Tuesday, February 23, 2010 7:01 AM To: [email protected] Subject: Adding different sized page volumes Greetings all, We need to add more page volumes (for both space and actuators) but are fresh out of 3390-9's. If we throw 3390-27's into the mix, should they be fully allocated as PAGE, or just cyls 1-10016? Will I start a religous war if I also ask about the latest recommendation for page volume space utilization? Max of 25%? 50%? "It Depends"? Best regards, Mark Wheeler UnitedHealth Group Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. Sign up now. Hotmail: Free, trusted and rich email service. Get it now. 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.
