[linux-lvm] mirror and snapshot incompatible

[Yoav]

I know how to do it through device-mapper.  I'm just worried that maybe 
there's a reason why lvm prevents it.  Are you aware of such reason, or 
is it safe?

Jonathan Brassow wrote:
> It is possible to do all the things you are asking through 
> device-mapper... but there is no easy way to do it.  (and LVM does not 
> yet have the capabilities to manage this yet either.)
>
>  brassow
>
> On Oct 27, 2008, at 9:28 PM, Yoav wrote:
>
>> According to lvcreate, a snapshot of a mirrored volume cannot be 
>> created ("Snapshots and mirrors may not yet be mixed").  However, 
>> devmapper does not seem to have the same limitation when used 
>> directly (not through lvm).
>>
>> Is there a current reason for lvcreate to enforce this rather harsh 
>> limitation?
>>
>> What are the risks I'm taking by manually creating a dm-snapshot from 
>> a dm-mirror device?  (of course I'm also replacing the dm-mirror 
>> device with a snapshot-origin of the actual dm-mirror device).
>>
>> If there is an actual reason for preventing this, what is the 
>> suggested way to consistently backup a mirror volume?  Is there a way 
>> to temporarily take one of the mirror "legs" (mimage devices)  
>> offline in order to back it up, and resync it later?
>>
>>   Yoav
>>
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>
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