I'd recommend you also look at using Emulated FBA devices as long as you are considering alternatives. They are defined as EDEVs under z/VM. when you compare the options. Know that the largest size devices is around 300 GB, I've forgotten the exact size. It's an option to be aware of for a number of reasons including multipathing and disaster recovery, if you need those, without the requirements that disk be defined as CKD. As already stated by Christian Paro, recognize the performance aspects between all of the options and the requirements of your workloads.
We currently use EDEV FBA devices for boot/root/swap and linux server managed FBA/SCSI for data LUNs, but continue to think about moving it all to EDEV FBA definitions. Craig Collins State of WI On Fri, Mar 11, 2011 at 12:00 PM, Christian Paro <[email protected]>wrote: > A full set of benchmarks for different disk technologies with z/VM: > > http://www.vm.ibm.com/perf/reports/zvm/html/520dasd.html > > On Fri, Mar 11, 2011 at 12:57 PM, Donald Russell <[email protected] > >wrote: > > > I currently have a dozen or so RHEL 5.6 zLinux running on multiple VM 6.1 > > (well, 5, but 6.1 RSN), on z10 processors. > > > > The largest (disk space) is about 3TB and is currently FBA/SCSI.... > > > > We're thinking of changing this to ECKD to take advantage of the SAP to > do > > the real IO, instead of IO being handled within zLinux itself. > > > > (We have other zLinux system using ECKD) > > > > On one hand using ECKD will get us some CPU cycles back due to more work > > being done by the SAP, but just recenly I heard that IO can be faster > > (higher throughput) with FBA/SCSI. > > > > I'm assuming there's no clear answer as to which is best, because like so > > many performance tuning things, the answer is always "it depends". > > > > But, what are other people doing? My experience so far seems to be that > the > > choice of SCSI or ECKD depends on the background of the people making the > > decision.... people with a s390 background are familiar with ECKD, people > > coming from a unix/linux background are familiar with SCSI.. > > > > Thank you > > > > ---------------------------------------------------------------------- > > 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/
