• Automatically migrate data according to frequency of user access and age:
– Increases the effective “value” of storage resources – Designed for automatic archiving (backup/recovery) – Not a new technology
Online storage
Nearline storage
Archival storage
Hierarchical Storage Management (HSM) tools automate the migration of data from one storage class to another based on how old the data is and how frequently users access it. Based on these criteria, the HSM application automatically migrates storage from online storage to nearline storage or to offline or archival storage. It can also migrate data back from nearline storage when a user requests the data. HSM applications were designed primarily to automate the process of archiving data. HSM applications leave a “stub” when a file is removed from the online file system. When the user application attempts to access the stub, the HSM application is automatically notified and begins the process of retrieving the data from nearline storage. This may or may not be a transparent process to the user.