On Mon, Sep 26, 2011 at 9:45 PM, Mark Woodward <[email protected]> wrote: > On 09/26/2011 07:17 PM, Edward Ned Harvey wrote: >> >> So, this all serves to rather emphasize my point, which is to say... >> (LVM) Create snapshot, mount it, monitor it with nagios or whatever, >> lvextend it, lvextend the filesystem, resize2fs, unmount and release >> snapshot... >> versus >> (ZFS, Netapp, Volume Shadow Services, etc.) Do nothing, and don't worry >> about it. It's all automatic and dynamic and just works. > > I don't think this is right. Running nagios on a snapshot would do nothing. > A snapshot is protected from change.
This is neither true in the logical nor physical sense with LVM. It was never true in a physical sense, in that the storage for the snapshot is slowly used up due to copy-on-write as applications write to the original copy of the filesystem. It's not true in the logical sense because LVM snapshots have actually been read/write for quite a while. A common usage pattern for this appears to be when you want multiple copies of essentially the same virtual machine image. You start with a single gold copy and then create writable snapshots for each virtual machine. Bill Bogstad _______________________________________________ Discuss mailing list [email protected] http://lists.blu.org/mailman/listinfo/discuss
