> > I'm sadly out of touch with mainframe hardware; it seems strange to me > > I can get 120 Gbyte disks for my PC and you folk are using 2.3 Gbyte > > drives on your mainframes. I know the theoretical limit is larger than > > that, and was back when S/360 was announced. > > > > > One advantage to the limited disk size is that since you can only > have one I/O active to a disk volume at one time, spreading data over many
Is that true for RAID? Why should it be true even for single disks? our ancient 3330s had four physical paths; put them on a caching controller (I don't think they'd been invented then, but never mind that detail) and you should be able to run two-four concurrent I/O operations to a single device, at least as seen by the host. > smaller volumes allows more I/Os to be active at the same time. This can > dramatically improve system I/O throughput. IBM even warns that using > 3390-9s can degrade performance, think what using a 3390-120Gigabyte would Back in those days some of us were suspicious of the enormous 3330-1 drives; more data under the heads of 2314s with equivalent storage capacity might balance out the faster drives, the argument went. > do! In the PC world, I believe you can see the same sort of effect by using > RAID0 across multiple volumes, versus one large volume. I've no experience of RAID; I gave those bonnie tests a fly and even my K6-2/500 eats the mainframe figures I saw a while ago, but I do have a different version of bonnie (the report looks different) on my IDE drives. However, if those mainframe figures are created on toys rather than real hardware I guess that's to be expected. -- Cheers John Summerfield Microsoft's most solid OS: http://www.geocities.com/rcwoolley/ Note: mail delivered to me is deemed to be intended for me, for my disposition. ============================== If you don't like being told you're wrong, be right!
