COW = copy on write so once a original block is going to be overwritten, its data is copied out and put into snapshot. ming On Sat, 2005-08-13 at 16:07 +0300, Imre Gergely wrote: > hi > > i created a snapshot of a lvm, like this: > > lvcreate -s -L +50G -p r -n backup /dev/mail/mail /dev/sda2 > > that is, a 50gb, read-only snapshot for /dev/mail/mail to the PV sda2. > the i did a lvdisplay -v > > --- Logical volume --- > LV Name /dev/mail/mail > VG Name mail > LV UUID jhjDsx-FvKT-zJer-uSc3-2rrb-eHaC-Af7jBq > LV Write Access read/write > LV snapshot status source of > /dev/mail/backup [active] > LV Status available > # open 1 > LV Size 150.22 GB > Current LE 4807 > Segments 1 > Allocation next free (default) > Read ahead sectors 0 > Block device 254:3 > > --- Logical volume --- > LV Name /dev/mail/backup > VG Name mail > LV UUID nQrrrx-cTN8-4lqX-op9F-1vDO-VJ1V-hbQlTU > LV Write Access read only > LV snapshot status active destination for /dev/mail/mail > LV Status available > # open 0 > LV Size 150.22 GB > Current LE 4807 > Segments 1 > Snapshot chunk size 8.00 KB > Allocated to snapshot 0.13% > Allocation next free (default) > Read ahead sectors 0 > Block device 254:6 > > how can i tell, how big is that snapshot i created? i know that it's > 50gb, but where can i see this information. and what is "Allocated to > snapshot"? that percentage is from the 50gb a allocated for the > snapshot? or from the origin LV ? > > lvm> version > LVM version: 2.00.15 (2004-04-19) > Library version: 1.00.14-ioctl (2004-04-06) > Driver version: 4.4.0 > > > i installed lvm from CVS too, and i noticed the output of lvdisplay is a > bit different there. in fact, lvdisplay does not even show the snapshot > LV i created... if i do a vgdisplay -v, only then appears: > > --- Logical volume --- > LV Name /dev/test/root > VG Name test > LV UUID wqoG5m-X3Fn-Gsaj-8P9t-cSwS-AXi4-IJ5j2P > LV Write Access read/write > LV snapshot status source of > /dev/test/backup_root [active] > LV Status available > # open 1 > LV Size 976.00 MB > Current LE 244 > Segments 1 > Allocation inherit > Read ahead sectors 0 > Block device 253:3 > > --- Logical volume --- > LV Name /dev/test/backup_root > VG Name test > LV UUID cHs3wn-EUJl-f1wq-R8SJ-kpxZ-u9CG-L9Qhy1 > LV Write Access read only > LV snapshot status active destination for /dev/test/root > LV Status available > # open 0 > LV Size 976.00 MB > Current LE 244 > COW-table size 1016.00 MB > COW-table LE 254 > Allocated to snapshot 2.05% > Snapshot chunk size 8.00 KB > Segments 1 > Allocation inherit > Read ahead sectors 0 > Block device 253:2 > > lvm> version > LVM version: 2.01.13-cvs (2005-06-14) > Library version: 1.01.01 (2005-03-29) > Driver version: 4.4.0 > > > what's COW? :) > > thx. > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
