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Re: [linux-lvm] Snapshots and disk re-use




On 23/02/11 16:12, Ray Morris wrote:
On 23/02/11 14:16, Joe Thornber wrote:
  And how do I zero just exception store?

In this example, the normal lv is c1_s1.
It has two snapshots, c1_s1_snap0 and c1_s1_snap1.

List the underlying volumes like so:

[root clonebox2 ~]# ls -1  /dev/mapper/clones-c1_s1*
/dev/mapper/clones-c1_s1
/dev/mapper/clones-c1_s1-real
/dev/mapper/clones-c1_s1_snap0
/dev/mapper/clones-c1_s1_snap0-cow
/dev/mapper/clones-c1_s1_snap1
/dev/mapper/clones-c1_s1_snap1-cow

Half of those would be hidden to lvdisplay, though the man
page will probably tell you how to show hidden LVs.  "ls"
shows them all.

c1_s1_snap0-cow and c1_s1_snap1-cow are the copy on write
volumes, the exception stores, I believe.  -real is where
the current data lives, and c1_s1, the "main" LV is a basically
a proxy which reads directly from -rela, but diverts writes
so that old data is copied to -cow.  -snap0 is a proxy which
reads from either -cow or -real as needed.  Hopefully someone
will tell me where I'm wrong, if I am.

Zeroing c1_s1 first, then c1_s1_snap0-cow would zero everything,
Thanks for the explanation. But what if I don't want to zero everything? I only want to return everything back to the state it was before I created the snapshot.


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