[linux-lvm] Snapshots of snapshots are not supported yet

[markw at mohawksoft.com]

> Dne 8.7.2013 18:05, markw at mohawksoft.com napsal(a):
>> I'm trying to get a snapshot of a snapshot. I know the new thin
>> provisioning stuff supports this, but I'm not sure the release state is
>> something I can use at a customer.
>>
>> Using LVM2, the snapshot format is tried and true, but inefficient if
>> you
>> want to take multiple snapshots.
>>
>> Looking at dmsetup, there doesn't seem like there would be an issue
>> taking
>> a snapshot of a snapshot, but it is disabled in the tools.
>>
>> I guess my question is this: Can it be done? Is there any reason why it
>> should not work?
>>
>
> 1. Noone has written support for it in lvm2. And AFAICK noone is working
> on this.

I thought I saw a patch for this in the 2010 time frame.

>
> 2. Since the activation order of old snapshot is not as simple as with
> other
> targets, it's currently not so easy to add support for into lvm deptree
> resolver.

In my case I would, more or less, be maintaining a lot of the
interdependency information for the chain of shapshots and it would
managed by a daemon being controlled by an application, not really subject
to the whims of a sys admin.


Is there a stable and supported way of getting this functionality? FYI:
I'm trying to use RHEL as the basis for this and I think that's an old
2.6.x kernel.


>
> Zdenek
>
>
>
>