2.6.16.20/dm: can't create more then one snapshot of an lv

2.6.16.20/dm: can't create more then one snapshot of an lv

[CaT]

I am attempting to create multiple snapshots of an lv ontop of a raid-5
software raid device and ext3+dir_index and resize_inode for the fs.
The kernel is a pure 64bit compile with Debian Sarge amd64 running on
top of it. The kernel is monolithic and I'm using lvm2 2.01.03-5 with
devmapper 1.01.

This works under 2.6.15.7. Under 2.6.16.20 I get this:

# lvcreate --snapshot --size 50G --name snap-12 --permission r --verbose /dev/backups/main
    Setting chunksize to 16 sectors.
    Finding volume group "backups"
    Creating logical volume snap-12
    Archiving volume group "backups" metadata.
    Creating volume group backup "/etc/lvm/backup/backups"
    Found volume group "backups"
    Loading backups-snap--12
    Zeroing start of logical volume "snap-12"
    Found volume group "backups"
    Removing backups-snap--12
    Found volume group "backups"
    Found volume group "backups"
    Found volume group "backups"
    Loading backups-main-real
    Loading backups-snap--12-cow
    Loading backups-snap--12
    Loading backups-main
    Creating volume group backup "/etc/lvm/backup/backups"
  Logical volume "snap-12" created
# lvcreate --snapshot --size 50G --name snap-13 --permission r --verbose /dev/backups/main
    Setting chunksize to 16 sectors.
    Finding volume group "backups"
    Creating logical volume snap-13
    Archiving volume group "backups" metadata.
    Creating volume group backup "/etc/lvm/backup/backups"
    Found volume group "backups"
    Loading backups-snap--13
    Zeroing start of logical volume "snap-13"
    Found volume group "backups"
    Removing backups-snap--13
    Found volume group "backups"
    Found volume group "backups"
    Found volume group "backups"
    Loading backups-main-real
    Loading backups-snap--12-cow
    Loading backups-snap--12
*freeze*

# ps auxww | grep lvcreate
root      1315  0.0  1.2 16000 13104 pts/2   D<L+ 11:44   0:00 lvcreate --snapshot --size 50G --name snap-13 --permission r --verbose /dev/backups/main

Nothing special in dmesg at time of lvcreate.

# lsof -n | grep 1315 | less
lvcreate  1315        root  cwd       DIR                9,0    1024       4017 /root
lvcreate  1315        root  rtd       DIR                9,0    1024          2 /
lvcreate  1315        root  txt       REG                9,0  465896     116659 /lib/lvm-200/lvm
lvcreate  1315        root  mem       REG                0,0                  0 [heap] (stat: No such file or directory)
lvcreate  1315        root  mem       REG                9,0   90288     116481 /lib/ld-2.3.2.so
lvcreate  1315        root  mem       REG                9,1  290512     458029 /usr/lib/locale/locale-archive
lvcreate  1315        root  mem       REG                9,0   34640     116657 /lib/libdevmapper.so.1.01
lvcreate  1315        root  mem       REG                9,0   12072     116489 /lib/libdl-2.3.2.so
lvcreate  1315        root  mem       REG                9,0 1295328     116487 /lib/libc-2.3.2.so
lvcreate  1315        root    0u      CHR              136,2                  4 /dev/pts/2
lvcreate  1315        root    1u      CHR              136,2                  4 /dev/pts/2
lvcreate  1315        root    2u      CHR              136,2                  4 /dev/pts/2
lvcreate  1315        root    3u      CHR              10,63              44265 /dev/mapper/control
lvcreate  1315        root    4uW     REG              253,2       0     147459 /var/lock/lvm/V_backups
lvcreate  1315        root    5u      BLK                9,0              33555 /dev/md0
lvcreate  1315        root    6u      BLK                9,1              33567 /dev/md1
lvcreate  1315        root    7u      BLK                9,2              33568 /dev/md2
lvcreate  1315        root    8u      BLK                9,3              33569 /dev/md3

MD section of .config:

#
# Multi-device support (RAID and LVM)
#
CONFIG_MD=y
CONFIG_BLK_DEV_MD=y
# CONFIG_MD_LINEAR is not set
# CONFIG_MD_RAID0 is not set
CONFIG_MD_RAID1=y
# CONFIG_MD_RAID10 is not set
CONFIG_MD_RAID5=y
# CONFIG_MD_RAID6 is not set
# CONFIG_MD_MULTIPATH is not set
# CONFIG_MD_FAULTY is not set
CONFIG_BLK_DEV_DM=y
CONFIG_DM_CRYPT=y
CONFIG_DM_SNAPSHOT=y
CONFIG_DM_MIRROR=y
CONFIG_DM_ZERO=y
# CONFIG_DM_MULTIPATH is not set

This server is not live yet so I can test patches if need be. I wont be 
able to in approx 1 weeks time though.

-- 
    "To the extent that we overreact, we proffer the terrorists the
    greatest tribute."
    	- High Court Judge Michael Kirby

Re: 2.6.16.20/dm: can't create more then one snapshot of an lv

[CaT]

On Mon, Jun 19, 2006 at 12:00:40PM +1000, CaT wrote:
> I am attempting to create multiple snapshots of an lv ontop of a raid-5
> software raid device and ext3+dir_index and resize_inode for the fs.
> The kernel is a pure 64bit compile with Debian Sarge amd64 running on
> top of it. The kernel is monolithic and I'm using lvm2 2.01.03-5 with
> devmapper 1.01.
> 
> This works under 2.6.15.7. Under 2.6.16.20 I get this:

2.6.17 also fails.

More info: The failing kernels can deal with multiple pre-created
snapshots but the moment I try to create one it freezes as below. Mounting
another snapshotted volume at the time this is frozen freezes mount.

After reboot the snapshot it froze on making is available to the system
(though the reboot fails on shutdown as it cannot unmount anything).

> # lvcreate --snapshot --size 50G --name snap-13 --permission r --verbose /dev/backups/main
>     Setting chunksize to 16 sectors.
>     Finding volume group "backups"
>     Creating logical volume snap-13
>     Archiving volume group "backups" metadata.
>     Creating volume group backup "/etc/lvm/backup/backups"
>     Found volume group "backups"
>     Loading backups-snap--13
>     Zeroing start of logical volume "snap-13"
>     Found volume group "backups"
>     Removing backups-snap--13
>     Found volume group "backups"
>     Found volume group "backups"
>     Found volume group "backups"
>     Loading backups-main-real
>     Loading backups-snap--12-cow
>     Loading backups-snap--12
> *freeze*

-- 
    "To the extent that we overreact, we proffer the terrorists the
    greatest tribute."
    	- High Court Judge Michael Kirby

Re: 2.6.16.20/dm: can't create more then one snapshot of an lv

[Heinz Mauelshagen]

How many snapshots active at once ?
I guess this is a kcopyd scalability issue which needs addressing.

Regards,
Heinz    -- The LVM Guy --

On Tue, Jun 20, 2006 at 10:54:05AM +1000, CaT wrote:
> On Mon, Jun 19, 2006 at 12:00:40PM +1000, CaT wrote:
> > I am attempting to create multiple snapshots of an lv ontop of a raid-5
> > software raid device and ext3+dir_index and resize_inode for the fs.
> > The kernel is a pure 64bit compile with Debian Sarge amd64 running on
> > top of it. The kernel is monolithic and I'm using lvm2 2.01.03-5 with
> > devmapper 1.01.
> > 
> > This works under 2.6.15.7. Under 2.6.16.20 I get this:
> 
> 2.6.17 also fails.
> 
> More info: The failing kernels can deal with multiple pre-created
> snapshots but the moment I try to create one it freezes as below. Mounting
> another snapshotted volume at the time this is frozen freezes mount.
> 
> After reboot the snapshot it froze on making is available to the system
> (though the reboot fails on shutdown as it cannot unmount anything).
> 
> > # lvcreate --snapshot --size 50G --name snap-13 --permission r --verbose /dev/backups/main
> >     Setting chunksize to 16 sectors.
> >     Finding volume group "backups"
> >     Creating logical volume snap-13
> >     Archiving volume group "backups" metadata.
> >     Creating volume group backup "/etc/lvm/backup/backups"
> >     Found volume group "backups"
> >     Loading backups-snap--13
> >     Zeroing start of logical volume "snap-13"
> >     Found volume group "backups"
> >     Removing backups-snap--13
> >     Found volume group "backups"
> >     Found volume group "backups"
> >     Found volume group "backups"
> >     Loading backups-main-real
> >     Loading backups-snap--12-cow
> >     Loading backups-snap--12
> > *freeze*
> 
> -- 
>     "To the extent that we overreact, we proffer the terrorists the
>     greatest tribute."
>     	- High Court Judge Michael Kirby
> -
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=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Red Hat GmbH
Consulting Development Engineer                   Am Sonnenhang 11
Storage Development                               56242 Marienrachdorf
                                                  Germany
Mauelshagen@RedHat.com                            PHONE +49  171 7803392
                                                  FAX   +49 2626 924446
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Re: 2.6.16.20/dm: can't create more then one snapshot of an lv

[CaT]

On Tue, Jun 20, 2006 at 12:02:09PM +0200, Heinz Mauelshagen wrote:
> How many snapshots active at once ?

1. I can start more then 1 premade snapshots just fine and use them
but the moment I add another one a freeze occurs.

> I guess this is a kcopyd scalability issue which needs addressing.

Well in the end I'm hoping to get at least 7. Hopefully that's not
insane. :)

-- 
    "To the extent that we overreact, we proffer the terrorists the
    greatest tribute."
    	- High Court Judge Michael Kirby

Re: 2.6.16.20/dm: can't create more then one snapshot of an lv

[Heinz Mauelshagen]

On Tue, Jun 20, 2006 at 09:46:13PM +1000, CaT wrote:
> On Tue, Jun 20, 2006 at 12:02:09PM +0200, Heinz Mauelshagen wrote:
> > How many snapshots active at once ?
> 
> 1. I can start more then 1 premade snapshots just fine and use them
> but the moment I add another one a freeze occurs.

Well, that's fairly few ;)

> 
> > I guess this is a kcopyd scalability issue which needs addressing.
> 
> Well in the end I'm hoping to get at least 7. Hopefully that's not
> insane. :)

No, I was assuming, you were trying to activate plenty.

FYI: the snapshot code in 2.6.17-rc has received a fair amount of fixes
     which might help this vs. 2.6.16.20.

> 
> -- 
>     "To the extent that we overreact, we proffer the terrorists the
>     greatest tribute."
>     	- High Court Judge Michael Kirby

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Red Hat GmbH
Consulting Development Engineer                   Am Sonnenhang 11
Storage Development                               56242 Marienrachdorf
                                                  Germany
Mauelshagen@RedHat.com                            PHONE +49  171 7803392
                                                  FAX   +49 2626 924446
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Re: 2.6.16.20/dm: can't create more then one snapshot of an lv

[CaT]

On Tue, Jun 20, 2006 at 01:55:45PM +0200, Heinz Mauelshagen wrote:
> On Tue, Jun 20, 2006 at 09:46:13PM +1000, CaT wrote:
> > On Tue, Jun 20, 2006 at 12:02:09PM +0200, Heinz Mauelshagen wrote:
> > > How many snapshots active at once ?
> > 
> > 1. I can start more then 1 premade snapshots just fine and use them
> > but the moment I add another one a freeze occurs.
> 
> Well, that's fairly few ;)

Yes. I thought so too. :)

> > > I guess this is a kcopyd scalability issue which needs addressing.
> > 
> > Well in the end I'm hoping to get at least 7. Hopefully that's not
> > insane. :)
> 
> No, I was assuming, you were trying to activate plenty.

Not yet. Though as I said I plan to max out at 7 or so.

> FYI: the snapshot code in 2.6.17-rc has received a fair amount of fixes
>      which might help this vs. 2.6.16.20.

I tried 2.6.17 and I get the same issue. Any other kernel you want me to
try? I can reboot this box at will at the moment and test.

-- 
    "To the extent that we overreact, we proffer the terrorists the
    greatest tribute."
    	- High Court Judge Michael Kirby

Re: 2.6.16.20/dm: can't create more then one snapshot of an lv

[Alasdair G Kergon]

On Mon, Jun 19, 2006 at 12:00:40PM +1000, CaT wrote:
> I am attempting to create multiple snapshots of an lv ontop of a raid-5
> software raid device and ext3+dir_index and resize_inode for the fs.
> The kernel is a pure 64bit compile with Debian Sarge amd64 running on
> top of it. The kernel is monolithic and I'm using lvm2 2.01.03-5 with
> devmapper 1.01.
> This works under 2.6.15.7. Under 2.6.16.20 I get this:

Update to lvm2 version 2.02.01 or later and device-mapper version 1.02.02
or later.

Alasdair
-- 
agk@redhat.com

Re: 2.6.16.20/dm: can't create more then one snapshot of an lv

[CaT]

On Tue, Jun 20, 2006 at 03:20:05PM +0100, Alasdair G Kergon wrote:
> On Mon, Jun 19, 2006 at 12:00:40PM +1000, CaT wrote:
> > I am attempting to create multiple snapshots of an lv ontop of a raid-5
> > software raid device and ext3+dir_index and resize_inode for the fs.
> > The kernel is a pure 64bit compile with Debian Sarge amd64 running on
> > top of it. The kernel is monolithic and I'm using lvm2 2.01.03-5 with
> > devmapper 1.01.
> > This works under 2.6.15.7. Under 2.6.16.20 I get this:
> 
> Update to lvm2 version 2.02.01 or later and device-mapper version 1.02.02
> or later.

Done. It's all good under 2.6.16.20. Thanks for that. I'm wondering
though. I checked the minimal requirements in the
/usr/src/linux/Documentation/Changes file but nothing is mentioned for
LVM there. Is this no longer the right place to check for what userspace
utils are required for certain kernel functionality? (or was it never the
right place?)

-- 
    "To the extent that we overreact, we proffer the terrorists the
    greatest tribute."
    	- High Court Judge Michael Kirby