[linux-lvm] Snapshots

[Mark Woodward]

On 02/16/2012 10:43 AM, Mike Snitzer wrote:
> On Thu, Feb 16 2012 at  9:42am -0500,
> Mark Woodward<markw at mohawksoft.com>  wrote:
>
>> On 02/16/2012 08:57 AM, Mike Snitzer wrote:
>>> On Thu, Feb 16 2012 at  8:25am -0500,
>>> Mark Woodward<markw at mohawksoft.com>   wrote:
>>>
>>>> I have been looking into LVM2 for a while now and while I think it
>>>> is useful for a range of applications, its seems pretty limited in
>>>> overall scope.
>>>>
>>>> Is there any active development happening? Most of the code seems
>>>> like bug-fixes or minor tweaks. Is the snapshot system being
>>>> improved? Specifically, snapshots of snapshots? thin provisioned
>>>> snapshots or auto-expand (i.e. snapshots don't run out of space).
>>>> If you look at technologies like ZFS snapshots are far better
>>>> supported, but ZFS will probably never be real under Linux, and it
>>>> really is far more than is really needed.
>>>>
>>>> So, I guess my questions are these: Is LVM in maintenance mode or is
>>>> there active development? If it is being actively developed, is
>>>> there a road map and is there a group or site specifically dedicated
>>>> to the development?
>>> Um, where are you even getting this idea that LVM2 is in maintenance
>>> mode?  Or that snapshots haven't improved?
>>>
>>> Sorry to come off defensive but your entire post is founded on incorrect
>>> understanding.
>> Understood, I apologize.
>>> Anyway, if you look at the change history of the lvm2 repository (be it
>>> cvs or git, cvs commits are mirrored to git) you'll see there have been
>>> regular changes flowing in and most recently a very extensive evolution
>>> of the code to add support for thin provisioning with highly efficient
>>> snapshots (ala btrfs or ZFS).
>> I guess I missed that. I need to check out the changes, looks like
>> you have auto-grow with monitoring? I was looking more towards the
>> "snapshots of snapshots" ability. Is that on the radar?
> recursive snapshots of arbitrary depth (snapshot of snapshots ...) are
> already supported with the new thinp snapshots.
>
> Please review the upstream Linux>= 3.2 kernel code/docs too, it has
> more documentation of the underlying capabilities, e.g.:
>
> Documentation/device-mapper/thin-provisioning.txt
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/device-mapper/thin-provisioning.txt
>
> (the "Introduction" being the most approachable overview)
OK, that's where I missed it. I looked at the snapshots description. It 
is now part of thin-provisioning. Got it. Will it be in the 2.6 kernel 
or will there need to be an upgrade to 3.x series?