Resizing VM Disks

jojo · January 23, 2017, 5:38pm

Hi,

before I am starting to look into the VM states diagram and digging into scripts.

the docs describe that resizing vms at vm creation time here:
https://docs.opennebula.org/5.2/operation/vm_management/vm_instances.html

what does this sentence mean?

Increase the size of the disk container prior to launching the VM

the meaning of the second sentence is more obvious to me, it’s actually pretty clear:

Using the contextualization packages, at boot time the VM will grow the filesystem to adjust to the new size. This is only available for Linux guests in KVM.

so does “inceasing the size of disk container…” actually mean that it resizes a qcow file (or raw disk image) using qemu-img??

if yes, then this is not supposed to work on storage backends that don’t use qcow2 (or raw images). correct?

maybe someone can point me in the right direction.

thanks and all the best
Jojo

atodorov_storpool · January 24, 2017, 8:50am

Hi jojo,

Yes. It means resizing the device/file that is backing the VM disk.

Nope
It depend on the capabilities of the storage system and its TM_MAD driver.

AFAIK Currently the feature is for NON-PERSISTENT images only. The device resize is done in the TM_MAD/clone script. For CEPH it is here:

github.com

OpenNebula/one/blob/master/src/tm_mad/ceph/clone#L106


      
          EC_POOL_NAME="${XPATH_ELEMENTS[j++]}"
          
          disable_local_monitoring $DST_HOST $DST_DIR
          
          #-------------------------------------------------------------------------------
          # Clone the image and create @snap if it does not exists
          #-------------------------------------------------------------------------------
          
          if [ -n "$CEPH_USER" ]; then
              RBD="$RBD --id ${CEPH_USER}"
          fi
          
          if [ -n "$CEPH_KEY" ]; then
              RBD="$RBD --keyfile ${CEPH_KEY}"
          fi
          
          if [ -n "$CEPH_CONF" ]; then
              RBD="$RBD --conf ${CEPH_CONF}"
          fi
          
          if [ -n "$EC_POOL_NAME" ]; then

For qcow2 it is here:

github.com

OpenNebula/one/blob/master/src/tm_mad/qcow2/clone#L101


      
          elif [ "$FORMAT" = "qcow2" ]; then
              CLONE_CMD=$(qcow_dir_cmd $SRC_PATH $DST_PATH "create")
          else
              CLONE_CMD="cp $SRC_PATH $DST_PATH"
          fi
          
          CLONE_RESIZE_CMD=$(cat <<EOF
              $CLONE_CMD
              $RESIZE_CMD
          EOF
          )
          
          log "Cloning $SRC_PATH in $DST"
          ssh_exec_and_log "$DST_HOST" "$CLONE_RESIZE_CMD" "Error copying $SRC to $DST"
          
          exit 0

And for StorPool it is here:

github.com

OpenNebula/addon-storpool/blob/master/tm/storpool/clone#L78


      
              SP_TEMPLATE=
          else
              SP_TEMPLATE="${ONE_PX}-ds-$DS_ID"
          fi
          
          #-------------------------------------------------------------------------------
          # Action
          #-------------------------------------------------------------------------------
          
          storpoolVolumeCheck "$SP_VOL"
          
          storpoolVolumeClone "$SP_PARENT" "$SP_VOL" "$SP_TEMPLATE"
          
          if [ -n "$SIZE" ]; then
              if [ $SIZE -gt ${ORIGINAL_SIZE:-0} ]; then
                  storpoolVolumeResize "$SP_VOL" "$SIZE"M
              fi
          fi
          
          storpoolVolumeAttach "$SP_VOL" "$DST_HOST"

Hope this helps

Kind Regards,
Anton Todorov

jojo · January 25, 2017, 12:07pm

Yes Anton, it definitely helps! Great! Thank you!

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