On Dec 12, 2007 4:18 PM, Huegel, Thomas <[EMAIL PROTECTED]> wrote: > When I do this calculation I come up with a requirement of 10 3390 mod3 for > my page space. > I only have 2 3390 mod3's for page and I don't seem to be having any > problems.
When you run out of paging space, CP will abend typically faster than you can say Oops. The calculation does the worst case scenario when every user wants what you allowed him to have. Linux is that worst case. CMS users take what they need, Linux takes what you let it have. And I trust you also added the VDISKs to your calculation... If you only have 6 GB of paging space, it does not take that many users doing something unusual before you fill it up. Because Linux roughly uses the entire virtual machine size in a LRU fashion, at the moment it does not fit entirely in real memory, it will end up entirely on paging DASD. And not just that one Linux machine, but all of them because CP will take pages away from all of them. Even if you have not configured your paging DASD optimal, you can probably stand 1000 pg/s. That means that you fill the remaining 50% of your paging space in less than 10 minutes. Even if you have monitoring active on that, you still need to be pretty quick to beat that. Obviously, when you already have 25 GB of page space used at less than 50%, you would have a lot more time before bad things happen. Trust me, you would not be the first to abend because you run out of paging space. You know your workload and users best to estimate the chances that this may happen, and you know whether the investment in paging space is as insurance is justified. Rob PS I hear that some folks recommend to give each Linux server one of more real disks for swap that do not get used. Combined with the myth that swap space should be twice the virtual machine size, they end up with an unused disk of twice the virtual machine size. Clearly my choice would be to give it to CP as paging device... and let Linux (not) swap into VDISK. -- Rob van der Heij Velocity Software, Inc http://velocitysoftware.com/
