Snapshots
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?
Quoted 12 lines · Mark Woodward
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.
Quoted 4 lines
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.
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).
try: git clone git://sources.redhat.com/git/lvm2
take a look at the WHATS_NEW file and tell me what you think.
Mike
Hi Mike
Quoted 26 lines · Mike Snitzer
Quoted 12 lines · Mark Woodward
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.
Quoted 4 lines
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.
Quoted 8 lines
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).
try: git clone
git://sources.redhat.com/git/lvm2
Please, could you tell me if is there a gitweb interface somewhere?
Thanks
Marco
Quoted 36 lines · Marco Pizzoli
Hi Mike
Quoted 32 lines · Mike Snitzer
Quoted 12 lines · Mark Woodward
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.
Quoted 4 lines
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.
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).
Quoted 4 lines
Quoted 2 lines
try: git clone
git://sources.redhat.com/git/lvm2Please, could you tell me if is there a gitweb interface somewhere?
Quoted 19 lines · Mike Snitzer
Quoted 12 lines · Mark Woodward
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.
Quoted 4 lines
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?
Quoted 5 lines
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.
Quoted 5 lines
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?
Quoted 5 lines
try: git clone
git://sources.redhat.com/git/lvm2take a look at the
WHATS_NEWfile and tell me what you think.Mike
Long ago, Nostradamus foresaw that on Feb 16, Mark Woodward would write:
Quoted 1 line
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?
The ZumaStor 3rd party userland tools support that.
An elegant part of the LVM system is that the device mapper kernel support is very general, and new data structures can be experimented with entirely in user code - with a script language even. Metadata for experimental structures does not have to stored with the main metadata.
--
Stuart D. Gathman <[email protected]> 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.
Quoted 7 lines · Stuart D. Gathman
Long ago, Nostradamus foresaw that on Feb 16, Mark Woodward would write:
Quoted 3 lines
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?
The ZumaStor 3rd party userland tools support that.
Now AFAIK ZumaStor is a dead technology... nobody is actually maintaining the code upstream. The shared snapshot store that dm-thin-pool provides is functionally equivalent to what Zumastor provides -- dm-thinp provides a single storage pool for all snapshots. This avoids excessive copy-out that the old dm-snapshot suffered from due to it requiring a distinct snapshot store for each snapshot.
I'd really like to encourage you and others to evaluate and test snapshots with dm-thinp -- now that lvm2 provides support it _should_ be more approachable.
Quoted 4 lines
An elegant part of the LVM system is that the device mapper kernel support is very general, and new data structures can be experimented with entirely in user code - with a script language even. Metadata for experimental structures does not have to stored with the main metadata.
Please note that the dm-thinp code has metadata in the kernel (on-disk format for btrees, etc) much like a filesystem would have. So there is both kernel and userspace (lvm2) metadata for dm-thinp.
Mike
Long ago, Nostradamus foresaw that on Feb 16, Mike Snitzer would write:
Quoted 8 lines
Quoted 4 lines
An elegant part of the LVM system is that the device mapper kernel support is very general, and new data structures can be experimented with entirely in user code - with a script language even. Metadata for experimental structures does not have to stored with the main metadata.
Please note that the dm-thinp code has metadata in the kernel (on-disk format for btrees, etc) much like a filesystem would have. So there is both kernel and userspace (lvm2) metadata for dm-thinp.
Yes, but isn't this loaded into the kernel via userland tools like device-mapper? So while a kernel feature would be required for a new type of kernel metadata, experimental uses of existing formats can be done in userland.
--
Stuart D. Gathman <[email protected]> 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.
Quoted 7 lines · Stuart D. Gathman
Long ago, Nostradamus foresaw that on Feb 16, Mike Snitzer would write:
Quoted 5 lines
Quoted 4 lines
An elegant part of the LVM system is that the device mapper kernel support is very general, and new data structures can be experimented with entirely in user code - with a script language even. Metadata for experimental structures does not have to stored with the main metadata.
Quoted 6 lines
Quoted 3 lines
Please note that the dm-thinp code has metadata in the kernel (on-disk format for btrees, etc) much like a filesystem would have. So there is both kernel and userspace (lvm2) metadata for dm-thinp.
Yes, but isn't this loaded into the kernel via userland tools like device-mapper?
The 'thin-pool' and 'thin' DM device tables are loaded from userspace via DM interfaces.
The kernel metadata isn't loaded from userspace. It is created and/or changed by certain actions taken from userspace (via DM messages).
Quoted 3 lines
So while a kernel feature would be required for a new type of kernel metadata, experimental uses of existing formats can be done in userland.
The kernel manages the kernel's metadata. But the LVM metadata that userspace uses to coordinate and manage the thin devices can be changed independently.
The thin-provisioning-tools know the kernel's metadata format and can check it (and in the future repair it).
Quoted 7 lines · Stuart D. Gathman
Long ago, Nostradamus foresaw that on Feb 16, Mark Woodward would write:
Quoted 3 lines
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?
The ZumaStor 3rd party userland tools support that.
Has the zumastor stuff been updated lately? The last release I saw was nearly four years ago and the LVM2 and device-mapper capabilities have improved since.
Regards,
Bryn.
Quoted 27 lines · Mark Woodward
Quoted 19 lines · Mike Snitzer
Quoted 12 lines · Mark Woodward
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.
Quoted 4 lines
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?
Quoted 5 lines
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.
Quoted 8 lines
Quoted 5 lines
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
(the "Introduction" being the most approachable overview)
Quoted 40 lines · Mike Snitzer
Quoted 26 lines · Mark Woodward
Quoted 19 lines · Mike Snitzer
Quoted 12 lines · Mark Woodward
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.
Quoted 4 lines
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?
Quoted 5 lines
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.
Quoted 8 lines
Quoted 5 lines
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.
Quoted 8 lines
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(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?
Quoted 4 lines · Mark Woodward
Quoted 3 lines · Mike Snitzer
Please review the upstream Linux>= 3.2 kernel code/docs too, it has more documentation of the underlying capabilities, e.g.:
Quoted 8 lines
Quoted 5 lines
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?
It went upstream in Linux 3.2. So if using upstream kernels you'll need Linux >= 3.2. (you'll also need the latest upstream lvm2 code for the ability to create thinp devices and snapshots of them with lvm2).
But thinp will also be provided in the next RHEL6 release (6.3).
Mike