Re: [linux-lvm] Any way to speed up activation of volumes with snapshots?

[Chris Friesen <chris.friesen@windriver.com>]

On 09/14/2015 12:47 PM, Zdenek Kabelac wrote:
> Dne 14.9.2015 v 20:05 Chris Friesen napsal(a):
>> Hi,
>>
>> I'm running a 3.10 kernel with LVM 2.02.95.
>>
>> I'm running into a problem where activating snapshots can take quite a long
>> time, roughly one minute per 25GB of delta between the snapshot and the origin
>> volume.  (See below for my test procedure.)
>>
>> I realize that my kernel/LVM aren't exactly bleeding edge, and I wondering
>> whether more recent versions have done anything to speed up the activation
>> process (like maybe making it more lazy-loaded rather than reading in a bunch
>> of data up-front).
>>
>> If anyone is aware of such improvements, I'd appreciate it if you could point
>> me at the appropriate changes.
>
> Hi
>
> There is NO way to accelerate your existing setup, other then placing delta on
> SSD - the format of snapshot was meant to be used 'temporarily' - i.e. until you
> take backup of LV - but not for long-term multi-gigabyte case.
>
> This is major mis-use of this 'snapshot' feature - which repeats over and over...
>
> If you want to use long-living snapshots - you need to use thin-provisioning,

Thanks for the quick response.

Presumably we would still have multi-GB of delta between the original volume and 
the snapshot, so what would make the activation of a thin-provisioned snapshot 
faster?  Is the metadata stored differently?

Chris