On Tue, 31 Jan 2012 08:48:30 -0600, Mark Zelden <m...@mzelden.com> wrote:
>On Mon, 30 Jan 2012 22:35:02 +0000, Martin Packer <martin_pac...@uk.ibm.com> >wrote: > >> Because >>of the virtualisation within modern disk controllers robustness favours >>more, smaller. >> > >What 6-9 3390-27 page volumes isn't robust enough? :-) > >And regardless of PAV and where the physical location is on the emulated >DASD, if you put 5 smaller ones on _multiple_ mod-27s, isn't there more of >a chance some of them end up on the same physical disk(s). > >One thing this thread didn't cover are some of the performance >recommendations in the init and tuning guide related to large DASD. > >Recommendation #1, does say to only have one page data set per device. >and in the z/OS 1.11 manual I have open it even has the updated bars >on the left hand side. > >Writing to contiguous slots and over allocation is mentioned, but unless I >missed it the "old" ROT (and health check) of not having more than 30% >of the slots allocated is not specifically addressed. Certainly with 4K >pages (for the most part) and 3390-27 (or bigger) that 30% ROT doesn't >apply anymore? 50% of a mod-27 is still a helava lot of free slots. > Remove "(for the most part)" above - I momentarily forgot that 1M pages are not pageable. At least not now... -- Mark Zelden - Zelden Consulting Services - z/OS, OS/390 and MVS mailto:m...@mzelden.com Mark's MVS Utilities: http://www.mzelden.com/mvsutil.html Systems Programming expert at http://expertanswercenter.techtarget.com/ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
