Storage VMotion enables the migration of virtual machine storage volumes from one storage host to another with zero downtime. The benefits of this elimination of downtime for storage migration include:
- Non-Disruptive Movement of Storage across Device Types. VMotion works across all the types of storage that the ESX server “sees.” So, for example, storage volumes could be moved from internal direct attached disks to an iSCSI or Fibre Channel SAN while the VMs using those volumes continue to operate. Similarly, storage could be moved from one SAN array to another without disruption.
- Upgrading of Storage Assets. Normally when a storage array reaches end of life, there is necessary server downtime while data is migrated to a new storage array. With Storage VMotion, this migration can occur while the subject virtual servers continue to run.
- Storage Performance Optimization. To load balance storage I/O across storage devices, it may be necessary to move storage volumes among storage devices. This movement can be performed non-disruptively; however, it does not occur automatically with VMotion. Advanced planning will be necessary.
Though the potential of non-disruptive storage motion is real, implementers should take a careful and planned approach to using this technology. Migration time and processor/memory overhead make Storage VMotion a resource-intensive undertaking.