>>> On Thu, Feb 22, 2007 at 2:23 PM, in message <[EMAIL PROTECTED]>, Dave Hansen <[EMAIL PROTECTED]> wrote: -snip- > A). VM Memory Disk (VDISK). Currently we do not use VDISK for our > production zLinux servers on our z/VM 5.2 system. I see SLES 10 recommends > two > VDISKs. Is there a downside to using VDISK? About the only thing I saw is > that VDISK doesn't do expansion or contraction, so you may need to > "monitor" its usage. The popular thing I can see is to VDISK the swap > filesystem, which we don't do. It sounds to me that even if you only have > one > zLinux you want to use VDISK (at least for swap).
You probably don't want to use VDISK for files, just swap. As Marcy said (and others recommend as well), use two of them. Make the first one big enough for your expected use, and set an automation alert so that if the second one starts to get used, someone will investigate why. > B). Shared Kernel. This is an NSS and not just a DCSS for the filesystems > like "/var" (I think "/" or root is not supported in a DCSS anymore). So > this is what I IPL. If it's not there, I can't IPL. We have been kicking -snip- You probably don't want to mess with this just now. Later versions of the kernel, and crash dump, will support NSS better. You don't want to invalidate your support for it now. The kernel isn't that big, so sharing it among a few guests will buy you next to nothing. Using XIP2FS for /usr, and sharing it among your guests might be able to buy you quite a bit. Again, it depends on how many systems you're running. The more your run, the more you benefit. It takes some research to figure out exactly what to put into the DCSS for it, but as you grow, so will your savings. Look at the Cooperative Memory Management (CMM) stuff. In conjunction with swap on VDISK, you can dynamically "squeeze" a guest's virtual storage allocation. Using a good performance monitor (insert holy war here), you can determine the minimum amount of storage a guest needs without causing a performance impact from the paging. Barton Robinson says VDISKS can support up to 40,000 paging I/Os per second without a significant performance hit. Your mileage may vary (YMMV). Mark Post ---------------------------------------------------------------------- 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
