Patent ID: 7293133

Claim:
A system, comprising: a processor; and a memory comprising program instructions, wherein the program instructions are executable by the processor to implement: file system software configured to assign and migrate data in a multi-class file system comprising a hierarchy of storage classes, wherein the migrated data remains online within the multi-class file system, wherein one or more of the storage classes store data that is not modifiable but is readable by applications while the data is on the one or more storage classes, and wherein one or more others of the storage classes store data that is modifiable by applications while the data is on the one or more storage classes; and an application configured to perform an operation on data stored in the multi-class file system, wherein the operation requires stable data, wherein, to perform the operation, the application is configured to: perform the operation on at least one of the one or more storage classes that store data that is not modifiable without using a split mirror of the at least one of the one or more storage classes; and perform the operation on at least one of the one or more other storage classes that store data that is modifiable using a split mirror of the at least one of the one or more other storage classes.