>I am doing some tests with V-DISK used for swap space. >Is there advantages of using RESERVED V-DISK for swap space ? >I am using linux formatted V-DISK and it seems to work fine.
An FBA device like V-DISK already has (unlike CKD) already blocks of equal size so. Al you need to do is 'mkswap' to put the magic marker on it so that 'swapon' will like it. Some of us feel that there is a benefit to have VM already put that magic marker on so that Linux will find the disk prepared when it boots (instead of 'mkswap' in the rc.local or similar). If you have the disk CMS RESERVED it is very easy code to put the marker on, as I posted to the list some time ago. The other thing is that the Linux dasd driver decides on using the diagnose interface instead of SSCH, based on whether the disk is CMS RESERVED (incorrect, but that's how it is). In a number of scenario's the diagnose interface has performance benefit over SSCH issued by Linux. Unfortunately the diagnose discipline in the dasd driver was broken with 2.4.7 (supposed to be fixed with the mid-april patches on developerworks). So if you run 2.4.7 without the very latest patches, you must *not* make it CMS RESERVED to avoid that bug. Rob
