On Wed, Oct 14, 2009 at 10:52:19AM -0700, nate wrote: > James A. Peltier wrote: > > > Mounting a snapshot requires the generation of a new UUID for the file > > system in order to be able to use it. Perhaps this is a XFS limitation, > > but unlike ZFS they aren't immediately available. We need to perform this > > action extensively to backup file systems and allow for quick data > > recovery. > > Another side effect of snapshots and using LVM for example(applies > to any vendor's block based snapshots), is you can't easily take > a snapshot of an LVM-based file system, then mount that snapshot > on the same system, LVM will bitch. I spent some time trying to > play with dynamically changing the UUID in the volume group but > gave up, too complicated for my needs, instead I just mount the > snapshot on another system(or a VM with either Raw device mapping > in VMware or a software iSCSI initiator on the guest). > > I've written a few scripts for things like mysql snapshots and > Oracle snapshots over the years with my 3PAR array, using SSH > and key-based authentication the interface is pretty easy, a single > command to create a read-only snapshot, then another command > to create a read-write (read-write snapshots must be children of > read-only ones in the 3PAR world anyways). The process takes less > than a second, and if I want to snapshot a dozen volumes at the > same instant, still a single command and the array ensures all > volumes are taken at the same point in time, very helpful for > Oracle snapshots which can get messy if your dealing with > multiple volumes and not having them all perfectly in sync > with each other. > On Equallogic you can group your volumes, and snapshot the whole group. So it's meant exactly for this purpose; your database tables, logs and indices (and what not) are quaranteed to be snapshotted at the exact same time. -- Pasi