You need to remember that you can't start more than 1 I/O to an address (real or virtual!) at a time. This is a hardware restriction. This is why PAV was invented - so that the PAV alias addresses can be used to start parallel I/Os to the same base volume. So - if you don't have PAV, then it will not help to split up your mod 54 into minidisks. Linux may try to start more than 1 I/O at a time (since it can start one to each virtual address) but z/VM will only execute them one at a time and the other I/O requests will wait.
If you had HyperPAV, then splitting up the mod 54 into minidisks works, because then z/VM will use the PAV pool for that device to do I/Os to that device in parallel. If you have static PAV, the same thing also works, but the alias addresses have to be set up in advance. If you had SLES 10, then instead, I'd recommend that you define virtual PAV aliases to the guest with 1 minidisk and use multipath on Linux for overlapped I/O. But - this is not supported on SLES 9. On Thu, Mar 13, 2008 at 6:13 PM, Collinson.Shannon <[EMAIL PROTECTED]> wrote: > Yes, there is a partition on the volume. Sorry I wasn't clear about > that! > > So we need more than one minidisk even to set up the filesystem as > striped? I'd say that was our problem, except that I did try it without > striping (so it shows up as "1" for stripes in YaST2). > > We're not necessarily planning on a lot of data for single guests--it's > just that we'll be getting dasd on the VM lpar as mod54s (except for the > CP-OWNED volumes which will be mod9s). So single physical mod54s will > be carved up into multiple minidisks for several different guests. > > We might have PAV support in VM 5.3, but apparently (according to the > IBM storage guy we talked to last week), we either need to buy HiperPAV > (not gonna happen any time soon) or statically assign aliases in the > storage box to use it. The static alias assignment hasn't happened yet, > so I figure we "don't have PAV"... > -- Bruce Hayden Linux on System z Advanced Technical Support Endicott, NY ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
