Re: Use of RDB Kernel module

[Mike Lowe <j.michael.lowe@xxxxxxxxx>]

The ceph kernel module is only for mounting rbd block devices on bare metal (technically you could do it in a vm but there is no good reason to do so).  QEMU/KVM has its own rbd implementation that tends to lead the kernel implementation and should be used with vm's.

The rbd module is always used on a remote client and is never used inside a ceph cluster (comprised of mon,mds,osd).  

On Jul 2, 2013, at 3:19 PM, "Howarth, Chris " <chris.howarth@xxxxxxxx> wrote:

Hi – I am quite new to Ceph and would be grateful if you could explain a couple of items as these are not immediately clear to me from the Ceph documentation:

1) My Ceph cluster is running on RHEL 6.4 (kernel 2.6.32). As such I cannot use the RDB kernel module and so map block device images to the kernel module. I tried and this failed:

1.    rbd map fedbk --pool fed --name client.fed -m 10.40.99.165 -k /etc/ceph/lient.fed.keyring
FATAL: Module rbd not found.
rbd: modprobe rbd failed! (256)

Does this then mean that I cannot access these block devices from another server using libvirt/KVM ? i.e. it is not possible to use Ceph with libvirt/KVM etc unless I have a kernel level of 2.6.34 or later which supports the kernel module ?

2) Is the kernel RBD module ever used on a remote client ? For example the kernel CephFS module enable a client to remotely access and mount a CephFS filesystem. However it is not clear to me if there is a similar role for the RBD kernel module ? Can this be used to remotely access a remote block device - or is it only ever used on the Ceph cluster itself ?

thanks for your help.

Chris

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__________________________

Chris Howarth

OS Platforms Engineering

Citi Architecture & Technology Engineering

(e) chris.howarth@xxxxxxxx

(t) +44 (0) 20 7508 3848

(f) +44 (0) 20 7508 0964

(mail-drop) CGC-06-3A

 

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