[CentOS] question(s) about LVM snapshots

Tony Schreiner schreian at bc.edu
Fri Oct 12 14:35:14 UTC 2007

> When the snap shot volume is mounted, yes you can do df on it. But  
> that shows you the state of the volume you take the snapshot of at  
> the time of the snapshot. That's not what I want to know.

Sorry to answer my own question, but I just learned, lvdisplay shows  
the amount currently used by the snapshot

#lvdisplay /dev/vg_data/lv_backup
   --- Logical volume ---
   LV Name                /dev/vg_data/lv_backup
   VG Name                vg_data
   LV UUID                B0F6Gw-iVTt-jJ38-nFny-B2lF-QWei-hqJNlT
   LV Write Access        read/write
   LV snapshot status     active destination for /dev/vg_data/lv_data
   LV Status              available
   # open                 1
   LV Size                812.89 GB
   Current LE             208100
   COW-table size         143.45 GB
   COW-table LE           36724
   Allocated to snapshot  0.00%                        <<<<<--------
   Snapshot chunk size    8.00 KB
   Segments               1
   Allocation             inherit
   Read ahead sectors     0
   Block device           253:1


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