[linux-lvm] snapshot, machine hang and physical memory required

[Brian Weck]

I seem to be encountering a problem when attempting to create a 
snapshot. Sometimes the snapshot goes through fine and at other times 
while executing a 'lvcreate --snapshot ...' it subsequently causes my 
box to hang completely.

 From what I've read, this problem seems to be related to having 
insufficient physical memory.

I can not seem to find where/how to estimate how much memory is required 
to successfully perform the snapshot. Is the memory required relative to 
the snapshot size, the size of the target LVM device or both?

I'm running with a 2.6.12 kernel:
lvm2-2.01.14-2.0.RHEL4
device-mapper-1.01.04-1.0.RHEL4

As the machine seems to hang when creating a snapshot on "/" (rather the 
logical volume upon which "/" resides), upon a reboot I do not see 
anything in my logs related to the problem which further makes the 
problem harder to debug.

Any help would be greatly appreciated-
Brian