Dell PowerVault ME5 Series Administrator's Guide

Virtual storage

Virtual storage is a method of mapping logical storage requests to physical storage (disks). It inserts a layer of virtualization such that logical host I/O requests are mapped onto pages of storage. Each page is then mapped onto physical storage. Within each page the mapping is linear, but there is no direct relationship between adjacent logical pages and their physical storage.

A page is a range of contiguous Logical Block Addresses (LBAs) in a disk group, which is one of up to 16 RAID sets that are grouped into a pool. Thus, a virtual volume as seen by a host represents a portion of storage in a pool. Multiple virtual volumes can be created in a pool, sharing its resources. This allows for a high level of flexibility, and the most efficient use of available physical resources.

Some advantages of using virtual storage are:

• It allows performance to scale as the number of disks in the pool increases.
• It virtualizes physical storage, allowing volumes to share available resources in a highly efficient way.
• It allows a volume to be comprised of more than 16 disks.
• It enables you to easily add storage on the fly.

Virtual storage provides the foundation for data-management features such as:

• Automated tiered storage
• Read-cache disk groups
• Replication
• Quick rebuild
• Snapshots
• Overcommitting volumes
• Copying volumes or snapshots