[linux-lvm] Mounting a read only disk

Angel L. Mateo amateo at um.es
Tue Jan 28 12:34:20 UTC 2014

Hello guys,

     I'm having a problem I don't know how to solve.

     I have a running system with its disk under LVM2. Physical disks 
are in a SAN and we have no problems with them. Now we have configured 
an automated snapshots of our disks from our SAN to another one (both 
are HP 3par) and we want now the snapshot to be mounted in another 
system. This system has connected the snapshot disk without any problem 
but we can't mount the FS, because we can't activate volumes in it. The 
"only" difference between original disks and snaptshot ones are that 
this are seen by the OS as read only disks, so they can't be written.

     In the system trying to mount the snapshot I could see PVs, VGs and 
LVs, as:

amateo_adm at myotis52fa:~$ sudo pvs
   PV         VG          Fmt  Attr PSize    PFree
   /dev/sda5  Disk1       lvm2 a-      6.76g      0
   /dev/sdb   IndexesDisk lvm2 a-     69.98g  20.00g
   /dev/sdc   UsersDisk   lvm2 a-      2.50t      0
   /dev/sdd   UsersDisk   lvm2 a-   1023.98g 499.97g
amateo_adm at myotis52fa:~$ sudo vgs
   VG          #PV #LV #SN Attr   VSize  VFree
   Disk1         1   2   0 wz--n-  6.76g      0
   IndexesDisk   1   1   0 wz--n- 69.98g  20.00g
   UsersDisk     2   1   0 wz--n-  3.50t 499.97g
amateo_adm at myotis52fa:~$ sudo lvs
   LV          VG          Attr   LSize   Origin Snap%  Move Log Copy%  
   root        Disk1       -wi-ao 5.82g
   swap_1      Disk1       -wi-ao 956.00m
   vol_indexes IndexesDisk -wi-d- 49.98g
   vol_users   UsersDisk   -wi-d- 3.01t

     but I can't activate LVs:

amateo_adm at myotis52fa:~$ sudo lvchange -a y UsersDisk/vol_users
   device-mapper: reload ioctl failed: Invalid argument

     and in the logs I get:

Jan 28 13:32:41 myotis52fa kernel: [ 1789.845945] device-mapper: table: 
252:0: linear: dm-linear: Device lookup failed
Jan 28 13:32:41 myotis52fa kernel: [ 1789.846047] device-mapper: ioctl: 
error adding target to table

     the original system and the one trying to mount the snapshot are 
both ubuntu 12.04 with same kernel (3.4.0-030400-generic) and version of 
lvm2 (2.02.66-4ubuntu7.4, the packaged by ubuntu).

     Any help?

Angel L. Mateo Martínez	
Sección de Telemática
Área de Tecnologías de la Información
y las Comunicaciones Aplicadas (ATICA)
Tfo: 868887590
Fax: 868888337

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