>>> On 10/9/2012 at 06:50 PM, Brad Hinson <[email protected]> wrote: -snip- > I have lots of mod-9 ECKD with HyperPAV enabled, so I want to use LVM. So my > two choices are standard LVM, or LVM striping. If I stripe across the disks > I spread the I/O across the physical volumes, but my gut tells me I shouldn't > have to do this, since HyperPAV is moving around aliases dynamically. For > example, say I have 2 PVs and 4 HyperPAV aliases. If I send some heavy I/O > through the Linux (device-mapper) block device, then I would assume: > > - #1, for the case with LVM striping enabled, LVM will spread the I/O to both > PVs, and HyperPAV will assign 2 aliases to each PV since I'm banging on them > both. > - #2, for the case without LVM striping, HyperPAV will assign 4 aliases to > the first PV since that's the only one in use. > > In either case, it seems I'm using all 4 aliases, so seems like I would get > the same performance. Please correct me if I'm wrong. And if so, which of > these configs is better?
Keep in mind that performance is affected by how many real spindles the I/O is being issued against. A single real disk is only going to be able to do one seek, read, etc. at a time. Whether the storage admin took this into account creating the definitions for ECKD devices or not is another matter. But, if they did, and each volume is in a separate subsystem/rank/whatever within the storage array, then I would think that a combination of HyperPAV and striping would be able to eke out more I/Os than just one volume in one subsystem/rank/whatever. I leave it to the more knowledgeable members of the list to either confirm or disembowel this notion. :) Mark ---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
