Thin provisioning for shared block storage is of particular interest in the following cases:
- You want increased space efficiency. Images are sparsely and not thickly allocated.
- You want to reduce the number of I/O operations per second on your storage array. The GFS2 SR is the first SR type to support storage read caching on shared block storage.
- You use a common base image for multiple virtual machines. The images of individual VMs will then typically utilize even less space.
- You use snapshots. Each snapshot is an image and each image is now sparse.
- Your storage does not support NFS and only supports block storage. If your storage supports NFS, we recommend you use NFS instead of GFS2.
- You want to create VDIs that are greater than 2 TiB in size. The GFS2 SR supports VDIs up to 16 TiB in size.
The shared GFS2 type represents disks as a filesystem created on an iSCSI or HBA LUN. VDIs stored on a GFS2 SR are stored in the QCOW2 image format.