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Can I use an lvm snapshot to "undo" an rpm install ?

We have lots of  linux machines and little disk space.  

Most of our hosts are ESX although we have physical linux boxes also.

In the past we have installed rpm files that messed up the box and have problems getting them back up to get the rpm back off the box.

Can we do a lvm snapshot before and roll it back if there is a problem.  

As I understand a vmware ESX snapshot takes as much disk space as the original disk ( it is pretty much a mirror of the orignal machine ).   We have little disk space and clearly can not do the snapshot on the vmware side.  Snapshots on netapp filers take less than 1% of the disk space.  LVM snapshots likely fit somewhere between.  Does someone know how much space ( overhead ) a lvm snapshot takes

redhat linux 5.0

1 Solution
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Snapshots at a VMware level just tracks block changes. When a snapshot is created, changes are no l;onger written to the parent disk, but a child "delta" disk is created of the block changes that occur in the VM. Later when the snapshot is deleted, these are merged with the parent disk.

 I'm not sure where you have read VMware Snapshots equal original disk size. Maybe you have read this:-

Snapshot files can grow to the same size as the original base disk file, which is why the provisioned storage size of a virtual machine increases by an amount equal to the original size of the virtual machine multiplied by the number of snapshots on the virtual machine.


Can grow to a maximum size, but they start of at 100MB, and grow depending on block changes in the VM !

So it depends on how large the changes are in the VM, which are tracked.

BUT be warned if low on datastore space. Try it, create a snapshot, wait 60 seconds, and then delete it. (see the size!).

NetApp snapshots can be more efficient.

See my EE Article

HOW TO: VMware Snapshots :- Be Patient
TIMFOX123Author Commented:
ths works

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