On Mon, 2008-09-29 at 10:34 -0400, Jeff Darcy wrote: > > I just checked, and the current Lustre operations manual (v1.14, updated > September 19) does not seem to reflect that belief; even the "more > complex configurations" offer mkfs.lustre commands that give a combined > MGS/MDT.
But you will notice that in the specific section 4.2.2.6 "Running Multiple Lustre Filesystems" they do demonstrate setting up a separate MGS: An installation with two filesystems could look like this: mgsnode# mkfs.lustre --mgs /dev/sda mdtfoonode# mkfs.lustre --fsname=foo --mdt [EMAIL PROTECTED] /dev/sda ossfoonode# mkfs.lustre --fsname=foo --ost [EMAIL PROTECTED] /dev/sda ossfoonode# mkfs.lustre --fsname=foo --ost [EMAIL PROTECTED] /dev/sdb mdtbarnode# mkfs.lustre --fsname=bar --mdt [EMAIL PROTECTED] /dev/sda ossbarnode# mkfs.lustre --fsname=bar --ost [EMAIL PROTECTED] /dev/sda ossbarnode# mkfs.lustre --fsname=bar --ost [EMAIL PROTECTED] /dev/sdb Certainly it's not an absolute requirement, but for the corner case being discussed here, the need to reformat a filesystem -- the one co-located with the MGS, there is a problem. > In any case, my experience has been that customers are often > reluctant to carve a whole LUN out of their disk arrays for so little > data, Agreed. > and partitioning can have undesirable performance impacts. Also agreed. > Has > any consideration been given to ways of storing the MGS information > within a file on an existing filesystem instead of requiring on a > separate block device? How would that be any better than the co-located MGS/MDT situation where you want to reformat the filesystem that has the configuration information stored on it in a file? > I'm tempted to suggest doing this via the > loopback driver, since the MGS data-change rate is so low anyway. But you still have the problem of formatting that particular filesystem. I suppose you could umount the loopback device, copy the file to a different filesystem and remount the loopback device. That just seems cumbersome. I think a better proposal would be to enhance mkfs.lustre to save and restore the configuration data of the filesystems not being reformatted when a combination MGS/MDT is being formatted. Feel free to file a bugzilla ticket requesting that. b.
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