Sparse files are really bad... not only it takes ages to mkfs on them but you can get journal aborts and remounting the FS read-only under heavier disk load in the guest! Use them only for testing purposes and/or when you are really low on space. Daniel
_____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dave Costakos Sent: Monday, April 07, 2008 5:38 PM To: Red Hat Enterprise Linux 5 (Tikanga) discussion mailing-list Subject: [rhelv5-list] Xen Guest Disk Formatting Unfeasibly Slow I'm trying to troubleshoot a problem where mkfs commands take a really, really long time to complete in my Xen guests. I'm using sparse file-backed images created using the 'virt-install' command on RHEL 5.1 x86_64. I'm kickstarting paravirtualized RHEL 4.5 and 5.1 x86_64 guests and they are going through a standard, unattended install with a common diskmap. When they get to formatting the various local disks, all file system formats are taking unfeasibly long. A 20+ GB file system takes upwards of 20 minutes to run an mkfs on. During the mkfs, the underlying filesystem on the DOM0 shows high utilization via iostat (upwards on 99% utilization), but still the mkfs is horribly, horribly slow. mkfs is horribly slow whether I use a GFS, ext3 or NFS underlying filesystem, so I don't think that is the issue here. If I create a non-sparse disk image or a physical partition or logical volume, formatting times are drastically increased. However, I'm trying to be judicious with overall storage utilization and flexibility, I would very much like to stick with sparse files. Any advice on how I can troubleshoot this further or possibly find a solution? Is there another local disk driver I can use besides "tap:aio" (like "file") during the install process? Note: My underlying storage devices are Fibre Channel Hitachi OPEN-V*3 disks if it helps at all. -- Dave Costakos mailto:[EMAIL PROTECTED]
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