CP will page out to the disk with the best performance, so yes, the mdl3's may be filled too much when mixing sizes.
2010/9/30 O'Brien, Dennis L <dennis.l.o'br...@bankofamerica.com<dennis.l.o%27br...@bankofamerica.com> > > On of our z/VM 5.4.0 systems is about to grow to 140 GB of storage. Given > our target overcommit ratio of 3:1, and IBM's advice to keep paging space no > more than 50% full, this should just about fit onto 240 or 248 3390-3 sized > volumes. My question is what will happen the next time we add storage. > Clearly, we'll have to start using 3390-9 sized volumes for paging. Would > we be better off converting only enough volumes to satisfy the space > requirement, which would maximize the number of devices, or should we > convert all volumes to 3390-9 to keep them the same size? My concern is > that if we mix sizes, CP will try to allocate the same amount of space on > each volume, and the 3390-3's will get more than half full. On the other > hand, maximizing the number of devices maximizes the number of concurrent > I/O's. Our Storage people aren't going to give me 240 3390-9's if I don't > need them, so if I add another 32 GB of storage, my choice would be > something like 212 3390-3's and 28 3390-9's, or 100 3390-9's. Which would > be a better choice? > > Dennis > > "Decision" is not a verb. > -- Kris Buelens, IBM Belgium, VM customer support
