One of the benefits of striping is that you can do I/O in parallel, for example have 4 concurrent I/Os, so you reduce the "connect time" for transmission of data. Once the data gets to the end of the cable into the Storage Controller, it tends to be caught in cache, and should not matter what happens in the storage controller and onto the disk.
On Tue, 9 Mar 2021 at 21:45, Radoslaw Skorupka <[email protected]> wrote: > W dniu 09.03.2021 o 18:21, Paul Gilmartin pisze: > > On Tue, 9 Mar 2021 12:42:34 +0100, Radoslaw Skorupka wrote: > >> Striped PS datasets (extended format PS) are managed by IEBGENER, > >> ICEGENER or IDCAMS as regular (non-striped) datasets. I mean user > >> perspective. > >> > > In other words, transparent to the utility or user program, with at > > most changes to SMS profile? > Yes, you have to define it in SC. And use extended format. > > > What's the maximum performance boost? "Linear" can't mean > > "infinite". Limited by channel, main storage, controller cache ... > > bandwidth. (Model-dependent, of course.) > > It depends. I remember loooooong discussion (read: quarrel) with my > co-worker. It was 20+ years ago and it was about sense of striping on > RAMAC RVA. He was right. ;-) Striping gave some performance gain. I > can't remember exact values, but adding further stripes didn't help. > One may say for real (old gone) 3390 volumes the performance gain was > rather obvious, but bunch of volumes emulated on same hardware - > controller, disk RAID group - it should be no difference whether you use > one or several emulated volumes. However it is UNTRUE. Tested many times > on various disk system models. And sometime you can deep dive in disk > system details and create storage group consisting of volumes from > different RAID groups, possibly server by different controllers > (electronics). Modern arrays have quite reasonable features to support it. > And2: even volumes defined on exactly same physical resources perform > better when striping is in effect. > > > > This would appear to be a solution for the OP. Of course, unless > > he's already experiencing it, perhaps unbeknownst. > > Good to consider. However striping is the best for (long) sequential > read or write operations. > Last, but not least: it is easy to test. > > > BTW: Striping and multi-volume and extents is quite interesting issue > for quiz. ;-) > Things changed with the z/OS releases and the rules are different for > ef-PS and VSAM. > When I teach it on VSAM course, people usually forget about VSAM and > discuss about PS. > > -- > Radoslaw Skorupka > (looking for new job) > Lodz, Poland > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
