[linux-lvm] Strange snapshots behavior in dev/<vg>/

[linux-lvm] Strange snapshots behavior in dev/<vg>/

[Denny Schierz]

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hi,

to manage backups from Xen DomUs, I create snapshots from every guest.
They're all running under Debian Etch. No problem at all, normally, but
... see yourself:

My script creates only snapshots and mounts them, nothing more.

-----
root@henrietta ~ # /usr/local/bin/snap-mount.sh

  Logical volume "angelica-disk-snap" successfully removed
  Logical volume "hitomi-disk-snap" successfully removed
  Logical volume "rico-disk-snap" successfully removed
  Logical volume "triela-disk-snap" successfully removed
  Logical volume "zoe-disk-snap" successfully removed

Logical volume "angelica-disk-snap" created
/dev/neko/angelica-disk

Logical volume "hitomi-disk-snap" created
/dev/neko/hitomi-disk

Logical volume "rico-disk-snap" created
/dev/neko/rico-disk

Logical volume "triela-disk-snap" created
/dev/neko/triela-disk

Logical volume "zoe-disk-snap" created
/dev/neko/zoe-disk

root@henrietta ~ # ls /media/backup/angelica-disk/dev/neko/
hitomi-disk
----

So, first question, why i have the name from a different volume
(hitomi-disk) in the dev from angelica?


root@henrietta ~ # ls /media/backup/hitomi-disk/dev/neko
ls: /media/backup/hitomi-disk/dev/neko: Input/output error

Why i get here an error?


any suggestions?

root@henrietta ~ # uname -a
Linux henrietta 2.6.16.33-xen #1 SMP Mon Jan 8 14:39:02 GMT 2007 i686
GNU/Linux

root@henrietta ~ # dpkg -l | grep lvm
ii  lvm-common               1.5.20                          The Logical
Volume Manager for Linux (common
ii  lvm2                     2.02.06-4                       The Linux
Logical Volume Manager

root@henrietta ~ # dpkg -l | grep udev
ii  udev                     0.105-4                         /dev/ and
hotplug management daemo


LV display:

  --- Logical volume ---
  LV Name                /dev/neko/hitomi-disk
  VG Name                neko
  LV UUID                Tes7KH-pnv5-IGNt-vdf5-yCni-wSTo-dBd8ul
  LV Write Access        read/write
  LV snapshot status     source of
                         /dev/neko/hitomi-disk-snap [active]
  LV Status              available
  # open                 1
  LV Size                1.00 GB
  Current LE             256
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:2

  --- Logical volume ---
  LV Name                /dev/neko/hitomi-disk-snap
  VG Name                neko
  LV UUID                DIeQ81-Oeao-j9gt-RoRL-4G5L-0xko-Z5W9vN
  LV Write Access        read/write
  LV snapshot status     active destination for /dev/neko/hitomi-disk
  LV Status              available
  # open                 1
  LV Size                1.00 GB
  Current LE             256
  COW-table size         1.00 GB
  COW-table LE           256
  Allocated to snapshot  0.07%
  Snapshot chunk size    8.00 KB
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:25


  --- Logical volume ---
  LV Name                /dev/neko/angelica-disk
  VG Name                neko
  LV UUID                72Ibgz-WlBX-x0G2-6HlQ-MgB2-UOd2-n3aXSq
  LV Write Access        read/write
  LV snapshot status     source of
                         /dev/neko/angelica-disk-snap [active]
  LV Status              available
  # open                 1
  LV Size                4.00 GB
  Current LE             1024
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:10


  --- Logical volume ---
  LV Name                /dev/neko/angelica-disk-snap
  VG Name                neko
  LV UUID                fclDHb-U9Xb-wWQc-ptFH-jrNg-mNou-qzinbe
  LV Write Access        read/write
  LV snapshot status     active destination for /dev/neko/angelica-disk
  LV Status              available
  # open                 1
  LV Size                4.00 GB
  Current LE             1024
  COW-table size         1.00 GB
  COW-table LE           256
  Allocated to snapshot  0.09%
  Snapshot chunk size    8.00 KB
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:21

cu denny

-- 
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Re: [linux-lvm] Strange snapshots behavior in dev/<vg>/

[Stuart D. Gathman]

On Sat, 17 Nov 2007, Denny Schierz wrote:

> root@henrietta ~ # ls /media/backup/angelica-disk/dev/neko/
> hitomi-disk

Why would you do this?  device nodes in your backup still just point to
the device.  I suggest mounting your backup volumes with -o nodev,noexec both
to prevent possible security problems and to make it clear that the above
isn't useful.

> ----
> 
> So, first question, why i have the name from a different volume
> (hitomi-disk) in the dev from angelica?

Because hitomi-disk is the one that happens to be online at the moment.

> root@henrietta ~ # ls /media/backup/hitomi-disk/dev/neko
> ls: /media/backup/hitomi-disk/dev/neko: Input/output error

> Why i get here an error?

Because there isn't a disk online at the moment.

-- 
	      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.