> HI everyone. This post has created some confusion within my > VM group and I wanted to see if I understand XSTORE and MDC. > Linux does not utilize XSTORE for MiniDisk Cache
Actually, Linux really doesn't know much at all about XSTORE. Aside from the xpram device driver (for RAM disks), there's not much you can directly do with XSTORE in Linux. Linux does it's own cache in what it thinks is main storage. > and you are > better off using XSTORE for VM paging. Vastly better off. > Especially if you over > commit VDISK swap space. We tend to overcommit swap just by > the nature of how we clone. Actually, any time you force the VM system to exceed real resources. VDISK swap just happens to be one of the more convenient ways to do this when dealing with Linux guests. > VM's default setting assumes MDC > is meant to improve disk performance for VM guests. The defaults are somewhat OK for CMS guests. They're usually not so hot for guests that run other OSes. There's also the issue that Rob mentioned about I/O requests having to come from below the 2G line (so if a page needs to be physically paged out, it has to move below 2G to get the I/O done, which can lead to lots of thrashing). ---------------------------------------------------------------------- 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
