The StoreOnce VSA requires significant disk I/O for backup and recovery operations. The number, type and configuration of hard disks that provide capacity for the vdisks is an important choice. The number of disks and the type of disk will significantly effect the I/O potential and consequently backup and recovery performance. Consideration should be given to the design of the DataStores used for the vdisks for the StoreOnce VSA and the DataStores used to provide vdisks for other guests on the hypervisor. Ideally, the physical HDDs used for vdisks for the StoreOnce VSA should be isolated from the physical HDDs for the vdisks for other guests. The underlying HDDs should at least be configured in a RAID5 set for protection, particularly if backup data copy/replication is not used. It is also recommended that the effect of the resource consumption of the StoreOnce VSA on other virtual machines/applications running on the same pool of resources is assessed. This impact assessment should also consider any backup software components, running in virtual machines, which will require resources to execute backup and recovery jobs.