Read the z/VM performance reports. In general: with EDEVs you can sustain a somewhat higher page rate than with ECKD, but, the CPU cost to drive the paging operations is much higher per page (even with z/VM 5.3 which is better than 5.2).
2009/1/28 Bill Munson <[email protected]> > > Eric, > > What about using SCSI (edev) for z/VM PAGE packs ?? > > thanx > > Bill Munson > Brown Brothers Harriman > Sr. z/VM Systems Programmer > 201-418-7588 > > President MVMUA > http://www2.marist.edu/~mvmua/ <http://www2.marist.edu/%7Emvmua/> > > > > > *Eric R Farman <[email protected]>* > Sent by: The IBM z/VM Operating System <[email protected]> > > 01/27/2009 08:39 PM > Please respond to > The IBM z/VM Operating System <[email protected]> > > To > [email protected] cc > Subject > Re: Max EDEV size? > > > > > > Hi Lee, > > The biggest EDEV you can have is 1TB minus one page, with some exceptions > depending on the application of the EDEV: > > - DRCT, PAGE, SPOL allocations must reside in the first 64GB (minus one > page) of the volume > - CMS volumes are technically limited to 381GB, but will be less than > that in practice > > > More explanations can be found in Chapter 22 of the CP Planning and > Administration manual. > * > ** > http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/HCSG0B30/4.5.1?DT=20081120142224 > *<http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/HCSG0B30/4.5.1?DT=20081120142224> > > Regards, > Eric > > Eric Farman > z/VM I/O Development > IBM Endicott, NY > > > From: Lee Stewart <[email protected]> To: > [email protected] Date: 01/27/2009 07:50 PM Subject: Max EDEV > size? > > ------------------------------ > > > > I've looked, and maybe overlooked, but is there a maximum size for an > EDEV? LUNs on a SAN can be pretty big... Anyone know if it's > documented anywhere? > Thanks, > Lee > -- > > Lee Stewart, Senior SE > Sirius Computer Solutions > Phone: (303) 798-2954 > Fax: (720) 228-2321 > Email: [email protected] > Web: *www.siriuscom.com* <http://www.siriuscom.com> > > > ------------------------------ > > **************************** IMPORTANT NOTE ***************************** > The opinions expressed in this message and/or any attachments are those of > the author and not necessarily those of Brown Brothers Harriman & Co., its > subsidiaries and affiliates BBH. There is no guarantee that this message is > either private or confidential, and it may have been altered by unauthorized > sources without your or our knowledge. Nothing in the message is capable or > intended to create any legally binding obligations on either party and it is > not intended to provide legal advice. BBH accepts no responsibility for loss > or damage from its use, including damage from virus. > ******************************************************************** > -- Kris Buelens, IBM Belgium, VM customer support
