This is the third version of the shared exception store (based on Zumastor code). You can find the first and second submission: https://www.redhat.com/archives/dm-devel/2008-August/msg00003.html https://www.redhat.com/archives/dm-devel/2008-August/msg00087.html The major change since the second version is the snapshot deletion support. When you delete a snapshot, you can reclaim the disk spaces that it used. I would appreciate it if I could get comments on user interface, the changes to the existing code, etc though there are still several things to fix; the major one is disk format endian (Zumastor simply uses the CPU endian for the disk format). There are 9 patches and #1-6 patches include the changes to the existing code necessary to support the shared exception dm-snapshot. There are not any major changes to #1-6 patches since the last submission. The patches are available (against 2.6.28-rc2): http://www.kernel.org/pub/linux/kernel/people/tomo/dm-snap/2008-10-27/ If you like a git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tomo/linux-2.6-misc.git dm-snap = In this example, /dev/sda1 is used as an origin device and /dev/sdb1 is used as a cow device. - first, set up an origin and a cow: vine:/home/fujita# echo |dmesg create --notable work vine:/home/fujita# echo 0 `blockdev --getsize /dev/sda1` s-snap-origin /dev/sda1 /dev/sdb1 S 16|dmsetup load work vine:/home/fujita# dmsetup resume work - confirm the current status: vine:/home/fujita# dmsetup status work: 0 268430022 s-snap-origin : no snapshot - create one snapshot (the id is 0): vine:/home/fujita# dmsetup message work 0 snapshot create 0 - see if the snapshot is created: vine:/home/fujita# dmsetup status work: 0 268430022 s-snap-origin 1 0 - create one more snapshot (the id is 5) and see the result: vine:/home/fujita# dmsetup message work 0 snapshot create 5 vine:/home/fujita# dmsetup status work: 0 268430022 s-snap-origin 2 0 5 Note that creating a snapshot just means that you store some information on the cow device. You don't create a device for it yet. - create a device to access to the snapshot #5 vine:/home/fujita# echo |dmsetup create --notable snap5 vine:/home/fujita# echo 0 `blockdev --getsize /dev/sda1` s-snap /dev/sda1 5|dmsetup load snap5 vine:/home/fujita# dmsetup resume snap5 - confirm the current status: vine:/home/fujita# dmsetup status snap5: 0 268430022 s-snap Unknown work: 0 268430022 s-snap-origin 2 0 5 - remove the devices after you play with them: vine:/home/fujita# dmsetup remove snap5 vine:/home/fujita# dmsetup remove work vine:/home/fujita# dmsetup info No devices found - Again, setup the origin and the cow: vine:/home/fujita# echo |dmsetup create --notable work vine:/home/fujita# echo 0 `blockdev --getsize /dev/sda1` s-snap-origin /dev/sda1 /dev/sdb1 S 16|dmsetup load work vine:/home/fujita# dmsetup resume work vine:/home/fujita# dmsetup status work: 0 268430022 s-snap-origin 2 0 5 Note that you have two snapshots that you created. You can play with them again after creating devices for them. - delete the 5th snapshot vine:/home/fujita# dmsetup message work 0 snapshot delete 5 vine:/home/fujita# dmsetup status work: 0 268430022 s-snap-origin 1 0 *) By default, dmsetup perfomrs multiple tasks. I uses dmsetup commands that issue a single ioctl to make things clear. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
