Brad, I have seen some responses to your question, which raised questions. I will ignore the RVA, which works differently with its virtualisation. The latest DASD does reserve all the space for a specified volume. So allocating a 1 cylinder data set on a mod 27 would waste nearly all the space. With some of the copy functions you can get away with less for the copy, but not the original volumes. The data is striped across the raid DASD, so the real I/Os for a specific volume can be to different RAID DASD in parallel. So a mod 27 is not an issue here. One thing that would be an issue is if you did real RESERVEs and did not convert them to systems wide enqueues. You would be RESERVEing a lot of data from other systems. My major concern is the actual performance of a mod 27, irrespective of the type of data. If you put a lot of active data on a mod 27 then it will need more PAVs than a mod 3 or mod 9. I know you could have WLM managed dynamic PAVs. But the WLM addition of extra PAVs will lag behind an increase in I/O activity to a volume. The delays will be seen in IOSQ time. One solution is HIPERPAVs, which are only on the latest IBM DASD - these allocate PAVs from a pool as required rather than assigning to specific volumes. I do not think EMC have HIPERPAVs and do not know if they have committed to them and if so when. I think I would play safe for your new environment and put busy system data sets on smaller models than 27.
Terry Draper zSeries Performance Consultant [email protected] mobile: +966 556730876 --- On Mon, 18/5/09, Brad Wissink <[email protected]> wrote: From: Brad Wissink <[email protected]> Subject: System data sets and 3390-27 To: [email protected] Date: Monday, 18 May, 2009, 8:39 PM We are moving from a Shark with no PAV's to a EMC SAN with PAV's. We are going to use 3390-27's. I have read most of the archives on 3390-27's but I did not see anything on running your sysres or system data sets from a 27? We are thinking about going totally with 3390-27's, which means we must run with the sysres, jes checkpoint and spool, catalogues, RACF database, etc on the 27's. Is anyone doing that? What do we need to watch out for? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
