Sparse OVM virtual disks on appliances

For some reason, you may need to sparse OVM virtual disks in an Oracle appliances. Even though that feature is present trough the OVM Manager, most of the Oracle appliances doesn’t have any OVM Manager deployed on it. Therefore if you un-sparse your virtual disk by mistake, you are on your own.

This is a note on how to sparse virtual disks which are un-sparse.

Stop I/Os on the virtual disk

First, ensure the VM using the disk is stopped:
xm shutdown {VM_NAME}

For instance:
xm shutdown exac01db01.domain.local

Sparse disk


dd if={PATH_TO_DISK_TO_BE_SPARSED} of={PATH_TO_NEW_SPARSED_DISK} conv=sparsed


For instance:

dd if=/EXAVMIMAGES/GuestImages/exac01db01.domain.local/vdisk_root_01.img
of=/staging/vdisk_root_01.img
conv=sparsed


Move disk to former location

After the sparsing operation finished, copy the disk back to their former location:

# Retrieve the disks path:
cat /EXAVMIMAGES/GuestImages/{VM_NAME}/vm.cfg | grep disk
# Copy each disk back to its location:
mv /staging/{DISK_NAME}.img /EXAVMIMAGES/GuestImages/{VM_NAME}/{DISK_NAME}.img


For instance:

mv /staging/vdisk_root_01.img /EXAVMIMAGES/GuestImages/exac01db01.domain.local/vdisk_root_01.img


Start back the VM

Then you can start back the VM which use the new disk:
xm create /EXAVMIMAGES/GuestImages/{VM_NAME}/vm.cfg

I hope this helps and please contact us or comment below should you need more details.