Hello And thanks to everyone, I do appreciate everyone's input and opinions. We have the memory.
8 gig total, 5 gig defined for storage, 2 gig to xstore, and the rest used by the HMC. I do think that the problem is the MDC is only hitting 77-80% and the cpu gets driven up to 100%. It was at 92% before I do the SET MDC SYSTEM ON. I am weighting the overall results of the MDC to storage to CPU. This is a NOMAD2/ULTRAQUEST/TCPIP set of transactions. q xstore XSTORE= 2048M online= 2048M XSTORE= 2048M userid= SYSTEM usage= 51% retained= 0M pending= 0M XSTORE MDC min=0M, max=1024M, usage=49% XSTORE= 2048M userid= (none) max. attach= 2048M Ready; T=0.01/0.01 10:01:25 q store STORAGE = 5G Ready; T=0.01/0.01 10:01:59 ind AVGPROC-099% 01 XSTORE-000000/SEC MIGRATE-0000/SEC MDC READS-000488/SEC WRITES-000006/SEC HIT RATIO-077% STORAGE-012% PAGING-0001/SEC STEAL-000% Q0-00001(00000) DORMANT-00018 Q1-00000(00000) E1-00000(00000) Q2-00000(00000) EXPAN-001 E2-00000(00000) Q3-00005(00000) EXPAN-001 E3-00000(00000) PROC 0000-099% LIMITED-00000 Ed Martin Aultman Health Foundation 330-588-4723 [EMAIL PROTECTED] ext. 40441 > -----Original Message----- > From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On > Behalf Of Tom Duerbusch > Sent: Tuesday, July 11, 2006 3:06 PM > To: IBMVM@LISTSERV.UARK.EDU > Subject: Re: MDC, Storage, xstore, and cache on External dasd. > > Your concern is justified. > > The question is....real memory vs CPU. > > You shouldn't have much of an I/O bottleneck with your caching > controller, assumming you have ficon or better channel speeds. > > But if your read I/O is satisfied from MDC, you won't go thru the I/O > boundry which is a saving in CPU time. > > So the question becomes can you allocate sufficient real memory for MDC > in order to have a sufficiently high MDC read hit ratio, to have a real > savings in CPU? Or do you care about a few percent savings in CPU? > > If you are tight in main memory, it may be better to eliminate MDC and > use the memory to reduce paging. > If you are tight in CPU, then the CPU savings may be worth it. > > An old rule of thumb was caching closer to the application is better > than caching farther away from the application. But that is only if the > memory for caching was of equal sizes. I would rather have 6 GB > controller cache, then 2 MB for VSAM buffers. > > Anyway, I would experiment with MDC cache. If you can't get a high hit > ratio, say 95% or better, I would turn it off. But there is always > "that application" that may benefit greatly, for a short period of time, > by the use of MDC. > > Tom Duerbusch > THD Consulting > > >>> [EMAIL PROTECTED] 7/11/2006 1:27 PM >>> > Hello Everyone, > > I have found some time here to re-evaluate some parameters. > > We have a large amount of Cache (6 gig) on the EMC box. The > EMC > is doing lots of > caching. > > I am wondering about the overhead of the dual caching and the > benefits. > It seems to me that having MDC on for the system is just overhead and > dual caching. > > > z/VM side > q cache 740 > 0740 CACHE 0 available for subsystem > 0740 CACHE 1 available for subsystem > 06324150K Bytes configured > 06324150K Bytes available > 00000000K Bytes offline > 00000000K Bytes pinned > > 0740 CACHE activated for device > > VSE/ESA side > > cache subsys=740,status > AR 0015 SUBSYSTEM CACHING STATUS: ACTIVE > AR 0015 CACHE FAST WRITE: ACTIVE > AR 0015 CACHE STORAGE: CONFIG. ....... 6324150K > AR 0015 CACHE STORAGE: AVAIL. ....... 6324150K > AR 0015 NVS STATUS: AVAILABLE > AR 0015 NVS STORAGE: CONFIG. ....... 196608K > AR 0015 1I40I READY > > cache subsys=740,report > > AR 0015 3990-E9 SUBSYSTEM COUNTERS REPORT > > AR 0015 VOLUME 'RAM040' DEVICE ID=X'00' > > AR 0015 CHANNEL OPERATIONS > > AR 0015 <----SEARCH/READ----> > <-------------WRITE------------> > AR 0015 <----SEARCH/READ----> > <-------------WRITE------------> > AR 0015 TOTAL CACHE-READ TOTAL CACHE-WRITE > DASD-FAST > AR 0015 REQUESTS > > AR 0015 NORMAL 837170781 824709019 7467393 7463857 > 7467393 > AR 0015 SEQUENTIAL 13620747 13148843 168445 168286 > 168445 > AR 0015 CACHE FAST WRT 0 0 0 0 > N/A > AR 0015 > > AR 0015 TOTALS 850791528 837857862 7635838 7632143 > 7635838 > AR 0015 > > AR 0015 REQUESTS > > AR 0015 INHIBIT CACHE LOADING 0 > > AR 0015 BYPASS CACHE 31 > > AR 0015 > > AR 0015 DATA TRANSFERS DASD->CACHE CACHE->DASD > > AR 0015 NORMAL 9571687 762405 > > AR 0015 SEQUENTIAL 1600428 N/A > > AR 0015 1I40I READY > > > > > Ed Martin > Aultman Health Foundation > 330-588-4723 > [EMAIL PROTECTED] > ext. 40441