[linux-lvm] Snapshot behavior on classic LVM vs ThinLVM

[Zdenek Kabelac]

Dne 14.4.2017 v 09:20 Gionatan Danti napsal(a):
> Il 13-04-2017 14:41 Xen ha scritto:
>>
>> See, you only compared multiple non-thin with a single-thin.
>>
>> So my question is:
>>
>> did you consider multiple thin volumes?
>>
> 
> Hi, the multiple-thin-volume solution, while being very flexible, is not well 
> understood by libvirt and virt-manager. So I need to pass on that (for the 
> moment at least).
> 


Well since recent versions of lvm2  (>=169 , even though they are marked as 
exprimental) - do support script execution of a command for easier maintanence
of thin-pool being filled above some percentage.

So it should be 'relatively' easy to setup a solution where you can fill
your pool to i.e. 90% and if gets above - kill your surrounding libvirt,
and resolve missing resources (deleting virt machines..)

But it's currently impossible to expect you will fill the thin-pool to full 
capacity and everything will continue to run smoothly - this is not going to 
happen.

However there are many different solutions for different problems - and with 
current script execution - user may build his own solution - i.e.  call
'dmsetup remove -f' for running thin volumes - so all instances get 'error' 
device   when pool is above some threshold setting (just like old 'snapshot' 
invalidation worked) - this way user will just kill thin volume user task, but 
will still keep thin-pool usable for easy maintenance.

Regards

Zdenek