[ceph-users] Using RBD with LVM

John-Paul Robinson jpr at uab.edu
Tue Sep 24 17:00:09 PDT 2013


Hi,

I'm exploring a configuration with multiple Ceph block devices used with
LVM.  The goal is to provide a way to grow and shrink my file systems
while they are on line.

I've created three block devices:

$ sudo ./ceph-ls  | grep home
jpr-home-lvm-p01: 102400 MB
jpr-home-lvm-p02: 102400 MB
jpr-home-lvm-p03: 102400 MB

And have them mapped into my kernel (3.2.0-23-generic #36-Ubuntu SMP):

$ sudo rbd showmapped
id pool image            snap device
0  rbd  jpr-test-vol01   -    /dev/rbd0
1  rbd  jpr-home-lvm-p01 -    /dev/rbd1
2  rbd  jpr-home-lvm-p02 -    /dev/rbd2
3  rbd  jpr-home-lvm-p03 -    /dev/rbd3

In order to use them with LVM, I need to define them as physical
volumes.  But when I run this command I get an unexpected error:

$ sudo pvcreate /dev/rbd1
  Device /dev/rbd1 not found (or ignored by filtering).

I am able to use other RBD on this same machine to create file systems
directly and mount them:

$ df -h /mnt-test
Filesystem      Size  Used Avail Use% Mounted on
/dev/rbd0        50G  885M   47G   2% /mnt-test

Is there a reason that the /dev/rbd[1-2] devices can't be initialized as
physical volumes in LVM?

Thanks,

~jpr


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