[linux-lvm] snapshot pools, lvm roadmap

[linux-lvm] snapshot pools, lvm roadmap

[Brian Neu]

  For many years, I've greatly desired a snapshotting solution which goes above 
and beyond the current lvm features.  I'd love to see the ability to instantiate 
a storage pool for creating snapshots, with either a first-in-first-out or even 
some other method for bumping snapshots when the pool fills up.  The 
inefficiency of the former style of lvm snapshots in both space and speed and 
the cumbersome nature of managing them has kept me looking for alternatives. 
 Btrfs isn't quite there yet and may not be through 2011 or beyond.  zfs-fuse 
can't seem to act as a volume manager and I'm having problems with crashes. 
 Frustrated, I'm turning back to lvm.

   So now I'm looking at the lvm wiki and I'm seeing "shared exception store". 
 Can someone fill me in on the current status of this effort as the wiki was 
last updated in May-2009 ?

Thanks!

Re: [linux-lvm] snapshot pools, lvm roadmap

[Brian Neu]

So I'm seeing that this is actually 1 year to the day that Jonathan Brassow 
f/Red Hat wrote that shared snapshots was the current priority.

http://www.redhat.com/archives/linux-lvm/2010-January/msg00012.html

I believe that's the term for what I'm seeking.  Any update?



----- Original Message ----
> From: Brian Neu <proclivity76@yahoo.com>
> To: linux-lvm@redhat.com
> Sent: Wed, January 5, 2011 2:11:16 AM
> Subject: [linux-lvm] snapshot pools, lvm roadmap
> 
>   For many years, I've greatly desired a snapshotting solution which goes  
>above 
>
> and beyond the current lvm features.  I'd love to see the ability  to 
>instantiate 
>
> a storage pool for creating snapshots, with either a  first-in-first-out or 
>even 
>
> some other method for bumping snapshots when the  pool fills up.  The 
> inefficiency of the former style of lvm snapshots  in both space and speed and 

> the cumbersome nature of managing them has kept  me looking for alternatives. 
>  Btrfs isn't quite there yet and may not be  through 2011 or beyond.  zfs-fuse 

> can't seem to act as a volume manager  and I'm having problems with crashes. 
>  Frustrated, I'm turning back to  lvm.
> 
>    So now I'm looking at the lvm wiki and I'm seeing "shared  exception store". 
>
>  Can someone fill me in on the current status of this  effort as the wiki was 
> last updated in May-2009  ?
> 
> Thanks!
> 
> _______________________________________________
> linux-lvm  mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at  http://tldp.org/HOWTO/LVM-HOWTO/
> 

Re: [linux-lvm] snapshot pools, lvm roadmap

[Joe Thornber]

On Wed, 2011-01-05 at 10:34 -0800, Brian Neu wrote:
> So I'm seeing that this is actually 1 year to the day that Jonathan
> Brassow 
> f/Red Hat wrote that shared snapshots was the current priority.
> 
> http://www.redhat.com/archives/linux-lvm/2010-January/msg00012.html
> 
> I believe that's the term for what I'm seeking.  Any update? 

Shared snapshots is still top priority.  We ended up scrapping the first
design as it became apparent that people really wanted arbitrary depth
of recursive snapshots (snapshots of snapshots of snapshots ...) and we
hadn't allowed for that.

Currently myself and Heinz are working full time on the kernel side.
This includes a new metadata transaction library that will be used by
shared snaps, thin provisioning and hierarchical storage.  Expect an
experimental version of thin-provisioning sometime in January.  The
others should follow swiftly since they all have a lot of common code.
I'm not sure how long it will take to get from 'experimental' to
'production ready', obviously the more people that help us test, the
quicker this process will be.

- Joe

Re: [linux-lvm] snapshot pools, lvm roadmap

[Brian Neu]

> I'm not sure how long it will take to get from 'experimental'  to
> 'production ready', obviously the more people that help us test,  the
> quicker this process will be.


I have a God-given talent for breaking things Joe.  Let me know when there is a 
branch worthy of some testing and I'll give it a shot.  

Thanks for the update and good luck!

-Brian 

Re: [linux-lvm] snapshot pools, lvm roadmap

[Phillip Susi]

On 1/7/2011 2:33 PM, Brian Neu wrote:
>> I'm not sure how long it will take to get from 'experimental'  to
>> 'production ready', obviously the more people that help us test,  the
>> quicker this process will be.
> 
> I have a God-given talent for breaking things Joe.  Let me know when there is a 
> branch worthy of some testing and I'll give it a shot.  
> 
> Thanks for the update and good luck!

I've been wondering this myself.  I thought I found it over at
git.kernel.org/pub/scm/linux/kernel/git/agk/linux-2.6-dm.git/ but it
hasn't seen any updates in 4 months and has been fully merged into
Linus's tree.

Re: [linux-lvm] snapshot pools, lvm roadmap

[Alasdair G Kergon]

On Fri, Jan 07, 2011 at 03:27:27PM -0500, Phillip Susi wrote:
> I've been wondering this myself.  I thought I found it over at
> git.kernel.org/pub/scm/linux/kernel/git/agk/linux-2.6-dm.git/ but it
> hasn't seen any updates in 4 months and has been fully merged into
> Linus's tree.
 
I only update that when I have patches ready for Linus to pull.

The route for patches is:
  Email to dm-devel@redhat.com.

  Captured here:
    https://patchwork.kernel.org/project/dm-devel/list/?state=*
    (Patchwork state = New)

  Pulled into my working directory (quilt) here:
    http://www.kernel.org/pub/linux/kernel/people/agk/patches/2.6/editing/
and also copied here:
    ftp://sources.redhat.com/pub/dm/patches/2.6-unstable/editing/patches/
(sometimes kernel.org is slower syncing changes)
  (Patchwork state = Under Review)

  Pulled into linux-next git.
  (Patchwork state = Awaiting Upstream)

  Finally when a batch is ready to send to Linus, a branch is
created here:
  git.kernel.org/pub/scm/linux/kernel/git/agk/linux-2.6-dm.git/
for Linus to pull.

  Pulled into Linus's tree.
  (Patchwork state = Accepted + Archived)


Joe's patches aren't quite ready to enter this workflow yet.  But look out
for them on dm-devel soon.

Alasdair

Re: [linux-lvm] snapshot pools, lvm roadmap

[Joe Thornber]

On Fri, 2011-01-07 at 11:33 -0800, Brian Neu wrote:
> I have a God-given talent for breaking things Joe.  Let me know when
> there is a 
> branch worthy of some testing and I'll give it a shot.  

Are you interested in testing Thin Provisioning too?

- Joe

Re: [linux-lvm] snapshot pools, lvm roadmap

[Phillip Susi]

On 1/10/2011 5:15 AM, Joe Thornber wrote:
> Are you interested in testing Thin Provisioning too?

I certainly am.  I had been using snapshots with --virtualsize for this
to debug e2defrag.

Re: [linux-lvm] snapshot pools, lvm roadmap

[Stuart D. Gathman]

On Tue, 4 Jan 2011, Brian Neu wrote:

>   For many years, I've greatly desired a snapshotting solution which goes
>   above and beyond the current lvm features.  I'd love to see the ability to
>   instantiate a storage pool for creating snapshots, with either a
>   first-in-first-out or even some other method for bumping snapshots when the
>   pool fills up.  The inefficiency of the former style of lvm snapshots in
>   both space and speed and the cumbersome nature of managing them has kept me
>   looking for alternatives.  Btrfs isn't quite there yet and may not be
>   through 2011 or beyond.  zfs-fuse can't seem to act as a volume manager and
>   I'm having problems with crashes.  Frustrated, I'm turning back to lvm.
> 
>    So now I'm looking at the lvm wiki and I'm seeing "shared exception
>    store".  Can someone fill me in on the current status of this effort as
>    the wiki was last updated in May-2009 ?

These guys have snapshot pools working as an addon product.  It mostly
works using straight device mapper - but they have a kernel patch that is
needed for some deadlock issues.

http://zumastor.org/

-- 
	      Stuart D. Gathman <stuart@bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

Re: [linux-lvm] snapshot pools, lvm roadmap

[Brian Neu]

> These guys have snapshot pools  working as an addon product.  It mostly
> works using straight device  mapper - but they have a kernel patch that is
> needed for some deadlock  issues.
> 
> http://zumastor.org/
> 


Thanks Stewart, but the last update to their subversion repo was in Aug-2008. 
 It seems like a great solution, but I don't think I can put into production a 
possibly stale project without a significant user base.  Have you tried it?

I perform SMB consulting and when a Linux solution fits the client's needs, I 
always go with Linux.  But increasingly, I can't justify Linux file servers. 
 I've written some cron scripts that take and release lvm snapshots on a 
schedule, but compared to the Volume Shadow Copy of NTFS that Microsoft released 
in 2003, it's just cumbersome and basic.  We're approaching 8 years without a 
comparable response.  I'm just rather shocked when thinking about it.

Re: [linux-lvm] snapshot pools, lvm roadmap

[Phillip Susi]

On 1/5/2011 3:56 PM, Brian Neu wrote:
> I perform SMB consulting and when a Linux solution fits the client's needs, I 
> always go with Linux.  But increasingly, I can't justify Linux file servers. 
>  I've written some cron scripts that take and release lvm snapshots on a 
> schedule, but compared to the Volume Shadow Copy of NTFS that Microsoft released 
> in 2003, it's just cumbersome and basic.  We're approaching 8 years without a 
> comparable response.  I'm just rather shocked when thinking about it.

rsync-backup?

Re: [linux-lvm] snapshot pools, lvm roadmap

[Stuart D. Gathman]

On Thu, 6 Jan 2011, Phillip Susi wrote:

> On 1/5/2011 3:56 PM, Brian Neu wrote:
> > servers.  I've written some cron scripts that take and release lvm
> > snapshots on a schedule, but compared to the Volume Shadow Copy of NTFS
> > that Microsoft released 
> > in 2003, it's just cumbersome and basic.  We're approaching 8 years without
> > a comparable response.  I'm just rather shocked when thinking about it.
> 
> rsync-backup?

I'm not sure what "Volume Shadow Copy" actually does, but we use DRBD (Data
Replicating Block Device) to remotely mirror block devices - which could be
marketed as "Volume Shadow Copy".  

On local 1000BT lan, it supports transparent migration of Virtual Machines
between servers.  (Shared iSCSI is more often used for the purpose in an
enterprise, but DRBD is great for the poor man.)  

Remotely, it sends all block devices updates to a remote backup server - if
updates overwhelm the buffer, it switches to "sync" mode, then goes back to
sending all updates.

DRBD 8.3 comes with Fedora and with Centos-5.5 in the "extras" repository (and
presumably with EL5.5 also).  I see Debian and Ubuntu mentioned a lot in
support forums.

-- 
	      Stuart D. Gathman <stuart@bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

Re: [linux-lvm] snapshot pools, lvm roadmap

[Brian Neu]

> I'm not sure what "Volume Shadow Copy"  actually does, but we use DRBD (Data
> Replicating Block Device) to remotely  mirror block devices - which could be
> marketed as "Volume Shadow Copy". 
 
MS's VSS is their implementation of snapshots at the fs level.  For instance, 
you can set the C drive to back up to a D drive, allocating 80GB for all C drive 
snapshots.  Snapshots are removed automatically on a First-In, First-Out basis 
as the storage ceiling is reached.  Because the storage is shared, they can also 
be deduplicated for speed and storage efficiency.  Again, this has been in place 
since 2003.

As I understand LVM now, each snapshot must have individual storage allocated. 
 When that ceiling is reached, the snapshot must still be manually removed. 
 Since snapshot storage can't be shared, copied blocks must be written to every 
active snapshot, causing both a space and speed inefficiency.

I'm familiar with DRBD and have implemented it on HA systems.  It's great, but 
has nothing to do with the shared snapshots storage I desire for Linux.

Re: [linux-lvm] snapshot pools, lvm roadmap

[Stuart D. Gathman]

On Fri, 7 Jan 2011, Brian Neu wrote:

> > I'm not sure what "Volume Shadow Copy"  actually does, but we use DRBD (Data
> > Replicating Block Device) to remotely  mirror block devices - which could be
> > marketed as "Volume Shadow Copy". 
>  
> MS's VSS is their implementation of snapshots at the fs level.  For instance,
> you can set the C drive to back up to a D drive, allocating 80GB for all C
> drive snapshots.  Snapshots are removed automatically on a First-In,
> First-Out basis as the storage ceiling is reached.  Because the storage is
> shared, they can also be deduplicated for speed and storage efficiency.

Then the open equivalents would be Btrfs and Zumastor on LVM.  I think ZFS
does what you want also (and is enterprise ready on Solaris).

-- 
	      Stuart D. Gathman <stuart@bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

Re: [linux-lvm] snapshot pools, lvm roadmap

[Brian Neu]

> Are you interested in testing Thin Provisioning too?

> 
> -  Joe

Sorry for the slow response.  I typically only use this account for mailing 
lists only so I check it infrequently.

I'll script the most brutal tests I can, and I have very broad access to both 
on-metal and virtualized hosts.  Or if there is a FS testing controller app 
already written, I can use that too.  Just let me know what kind of stress you'd 
like to apply to it.