CephNotes

Some notes about Ceph
Laurent Barbe @CCM Benchmark

Ceph RBD Online Resize

Extend rbd drive with libvirt and XFS

First, resize the device on the physical host.

Get the current size :

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$ qemu-img info -f rbd "rbd:rbd/myrbd"

Be careful, you must specify a bigger size, shrink a volume is destructive for the FS.

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$ qemu-img resize -f rbd "rbd:rbd/myrbd" 600G

List device define for myVM :

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$ virsh domblklist myVM

Resize libvirt blockdevice :

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$ virsh blockresize --domain myVM --path vdb --size 600G
$ rbd info rbd/myrb

Extend xfs on guest :

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$ xfs_growfs /mnt/rbd/myrbd

Extend rbd with kernel module

You need at least kernel 3.10 on ceph client to support resizing. For previous version look at http://dachary.org/?p=2179

Get current size :

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$ rbd info rbd/myrbd

Just do :

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$ rbd resize rbd/myrbd --size 600000
$ xfs_growfs /mnt/rbd/myrbd

Also, since cuttlefish you can’t shrink a bloc device without specify additional option (–allow-shrink)

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