Progress on LVM2 snapshots
Dear all,
Please can anyone -authoritative- tell me about the current state of
snapshots support in LVM2? It was broken a while ago and I want to know if it has been fixed now. I am the author of a storage management project (www.openfiler.org), and we are currently stuck with LVM1 (and the RHEL3 2.4 kernel and hence smaller device sizes) due to non-working snapshots. Can LVM2 snapshots now be created and used reliably?
Mukund
yes, i believe now a lot of people has this question now.
is this question
1) very hard to solve technically. or
2) not so easy but doable, just no time and human resource?
thanks!
Ming
Quoted 18 lines · Mukund
Dear all,
Please can anyone -authoritative- tell me about the current state of
snapshots support in LVM2? It was broken a while ago and I want to know if it has been fixed now. I am the author of a storage management project (www.openfiler.org), and we are currently stuck with LVM1 (and the RHEL3 2.4 kernel and hence smaller device sizes) due to non-working snapshots. Can LVM2 snapshots now be created and used reliably?Mukund
_______________________________________________
linux-lvm mailing list
[email protected]
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
#2
I know agk had some plans for cleaning up single machine snapshots, but he is backed up behind reviewing/working on multipath and mirroring (in addition to traveling all over for conferences:).
brassow
Quoted 38 lines · Ming Zhang
yes, i believe now a lot of people has this question now.
is this question
1) very hard to solve technically. or
2) not so easy but doable, just no time and human resource?thanks!
Ming
Quoted 13 lines · Mukund
Dear all,
Please can anyone -authoritative- tell me about the current state of
snapshots support in LVM2? It was broken a while ago and I want to know if it has been fixed now. I am the author of a storage management project (www.openfiler.org), and we are currently stuck with LVM1 (and the RHEL3 2.4 kernel and hence smaller device sizes) due to non-working snapshots. Can LVM2 snapshots now be created and used reliably?Mukund
Quoted 5 lines
_______________________________________________
linux-lvm mailing list
[email protected]
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/_______________________________________________
linux-lvm mailing list
[email protected]
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
Thanks a lot for this information.
Is there anything external people like us can do to speed up this? There are many people waiting for this snapshot feature since it is so useful and essential. frankly, i know there are plan to replace md with dm, but since md is already stable and this snapshot is very unstable, why not do this first? :P
Ming
Quoted 51 lines · Jonathan E Brassow
#2
I know agk had some plans for cleaning up single machine snapshots, but he is backed up behind reviewing/working on multipath and mirroring (in addition to traveling all over for conferences:).
brassow
Quoted 40 lines · Ming Zhang
yes, i believe now a lot of people has this question now.
is this question
1) very hard to solve technically. or
2) not so easy but doable, just no time and human resource?thanks!
Ming
Quoted 15 lines · Mukund
Dear all,
Please can anyone -authoritative- tell me about the current state of
snapshots support in LVM2? It was broken a while ago and I want to know
if it has been fixed now. I am the author of a storage management project (www.openfiler.org), and we are currently stuck with LVM1 (and the RHEL3 2.4 kernel and hence smaller device sizes) due to non-working
snapshots. Can LVM2 snapshots now be created and used reliably?Mukund
Quoted 5 lines
_______________________________________________
linux-lvm mailing list
[email protected]
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/_______________________________________________
linux-lvm mailing list
[email protected]
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
Quoted 1 line · Ming Zhang
Thanks a lot for this information.
np
Quoted 1 line
Is there anything external people like us can do to speed up this?
1) File detailed bug reports
2) complain on this list
3) submit patches
Quoted 5 lines
There
are many people waiting for this snapshot feature since it is so useful and essential. frankly, i know there are plan to replace md with dm, but since md is already stable and this snapshot is very unstable, why not do this first? :P
The squeaky wheel gets the grease. Right now, multipath, [cluster] mirroring have been getting all the attention at the expense of single machine snap-shot. Hopefully, we can get snapshots soon.
brassow
Quoted 18 lines · Jonathan E Brassow
Quoted 1 line · Ming Zhang
Thanks a lot for this information.
np
Quoted 1 line
Is there anything external people like us can do to speed up this?
1) File detailed bug reports
2) complain on this list
3) submit patchesQuoted 6 lines
There
are many people waiting for this snapshot feature since it is so useful and essential. frankly, i know there are plan to replace md with dm, but
since md is already stable and this snapshot is very unstable, why not do this first? :P
Quoted 4 lines
The squeaky wheel gets the grease. Right now, multipath, [cluster] mirroring have been getting all the attention at the expense of single machine snap-shot. Hopefully, we can get snapshots soon.
:P u are rite. this is the truth. when both are important, loud voice gains.
Quoted 7 lines
brassow
_______________________________________________
linux-lvm mailing list
[email protected]
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
Quoted 2 lines · Ming Zhang
1) very hard to solve technically. or
2) not so easy but doable, just no time and human resource?
The hardest part of the fix involves changing the sequence of device-mapper ioctls that LVM2 uses, and that's a couple of weeks' development work, now pencilled into the RHEL4 Update 3 timescale.
In the meantime, you can apply the snapshot patches in the -udm tree and use 'dmsetup' manually to activate and deactivate snapshots when lvm2 fails.
Patches 8 and 9 at:
ftp://sources.redhat.com/pub/dm/patches/2.6-unstable/2.6.12-rc2/2.6.12-rc2-udm1/
(Further patches are needed, but those two plus correct dmsetup use should avoid machine lockups.)
Alasdair
Signature · 1 line
[email protected]
thanks!
so when is the RHEL4 Update 3 timescale? :)
will try the patches u mentioned.
ming
Quoted 18 lines · Alasdair G Kergon
Quoted 2 lines · Ming Zhang
1) very hard to solve technically. or
2) not so easy but doable, just no time and human resource?The hardest part of the fix involves changing the sequence of device-mapper ioctls that LVM2 uses, and that's a couple of weeks' development work, now pencilled into the RHEL4 Update 3 timescale.
In the meantime, you can apply the snapshot patches in the -udm tree and use 'dmsetup' manually to activate and deactivate snapshots when lvm2 fails.
Patches 8 and 9 at:
ftp://sources.redhat.com/pub/dm/patches/2.6-unstable/2.6.12-rc2/2.6.12-rc2-udm1/
(Further patches are needed, but those two plus correct dmsetup use should avoid machine lockups.)Alasdair