In the case of a minidisk allocated from an EDEVICE -- you only have a single path to work with on the Linux guest...
z/VM will use multipathing for the EDEVICE to handle IO requests coming from several guests/minidisks using the EDEVICE -- but each guest can only queue one io on each minidisk allocated from the EDEVICE (there is only a single address for the minidisk). If you want to have true multipathing at the Linux level - you'll have to use directly attached FCP subchannels... Scott Rohling On Tue, Apr 28, 2015 at 8:10 AM, Sergey Korzhevsky <[email protected]> wrote: > Hi Rob, > > Do i understand you right, that there is no performance boost in case > of multipathing EDEV, only failover? > In Linux, we have both, am i corect? > > Thank you. > > WBR, Sergey > > > > > Rob van der Heij <[email protected]> > Sent by: Linux on 390 Port <[email protected]> > 28-04-15 17:49 > Please respond to Linux on 390 Port > > To: [email protected], > cc: > Subject: Re: VM EDEVICE multipath for Linux > > > On 28 April 2015 at 16:38, Sergey Korzhevsky <[email protected]> wrote: > > Any idea why " The Virtualization Cookbook for IBM z/VM 6.3, RHEL 6.4, and > > SLES 11 SP3" (latest, i think) does not mention this setup? > > Maybe there some hidden problems? > > > > > One of the challenges is performance, since there's only one I/O at a time > on an EDEV disk. If you're doing very large disks, that can get a > bottleneck. Some installations use EDEV for the operating system and the > application code (to simplify provisioning) and use native FCP for the > application data (if any). > > Rob > > ---------------------------------------------------------------------- > 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/ > > > ---------------------------------------------------------------------- > 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/ > ---------------------------------------------------------------------- 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/
