Some applications require storage to be shared between servers. Red Hat Virtualization allows you to mark virtual machine hard disks as Shareable and attach those disks to virtual machines. That way a single virtual disk can be used by multiple cluster-aware guests.
Shared disks are not to be used in every situation. For applications like clustered database servers, and other highly available services, shared disks are appropriate. Attaching a shared disk to multiple guests that are not cluster-aware is likely to cause data corruption because their reads and writes to the disk are not coordinated.
You cannot take a snapshot of a shared disk. Virtual disks that have snapshots taken of them cannot later be marked shareable.
You can mark a disk shareable either when you create it, or by editing the disk later.