The trend of data growth continues to be alarmingly strong while managing large amount of storage capacity is getting more and more expensive. Data protection and file sharing are priority one issues. One of the biggest challenges is how to classify and manage diverse data while at the same time assuring uninterrupted access and conformance with existing policies. Solutions for business data protection and storage challenges are diverse and not always compatible. Among different methods on reducing the costs of data storage and facilitating data management tasks is Hierarchical Storage Management.
HSM simplifies and optimizes data storage by providing an automated transfer of less frequently used data from primary storage to less expensive secondary storage, such as magnetic tapes. Migration of data is based on business policies and performance requirements. When data is migrated, only a file stub remains on the primary storage that appears online to the user, regardless of whether it is stored online, near-line or offline. When needed, the original data is recalled back from secondary to the primary storage.
The stub retains file’s original metadata, e.g., last-modified time and size, but does not contain any of the original data contents.
HSM as a complementary solution to other data protection methods
|Comparison of storage strategies||Backup||HSM||Archive|
|How does it work?||Protecting data by producing secondary copy of data for cases of data loss||Migrating less frequently used data from primary to more cost-effective storage||Keeping data in secondary storage for preserving data content and complying with legal regulations|
|What is stored?||Active data, entire file systems||Less frequently used data||Inactive data for long-term retention|
|What happens to the original data?||Stays as is in primary storage||Stub (metadata with pointers) left in primary storage, data content moved to secondary storage||Original usually deleted from the primary storage|
|How is data recalled?||In the event of a failure of online data, it is restored by the administrator||The data appears to be online, seamless access for a user||If the data is required by users or for legal purposes, the administrator can retrieve it|
|What storage infrastructure?||Quickly accessible, meet performance needs
||Combined/tiered storage for automated transfer of data from online to secondary/near-line storage (e.g., easily retrievable tape or writable optical)||Low-cost, high capacity and durability cold storage|
SEP sesam's HSM-aware backup for Windows
HSM-aware backup for Windows is provided by default as part of a SEP sesam package. SEP sesam provides efficient backup of data on Windows systems that is managed by HSM. HSM detects data that has not been accessed in a long period of time and migrates such inactive data to lower-cost nearline storage, leaving only small stub files in the original location on the primary storage.
SEP sesam as an HSM-aware solution recognizes the reparse tags in stub files and does not trigger a recall of the original files, but performs a backup of the placeholder files without retrieving their contents. The backed up stub files can then be restored as any other data to the same location or to a new restore target. If the stub files are going to be restored to a new host, the new host must have the HSM software installed in order to correctly interpret restored reparse points.
SEP sesam also provides an option –o follow which allows backing up a complete migrated file rather than just a stub. Typically, this option should not be used for backing up the whole volumes which were migrated to another storage tier as this would mean that the whole archive is recalled and backed up causing unwanted space consumption on the primary storage and HSM performance issues.
The –o follow option should only be used for exceptions – to back up specific data, e.g., files that are of a high importance and need a complete backup copy to be saved in a backup pool. It is also recommended to use this option only once to perform a full backup and later on perform only ordinary HSM-aware backups (without the –o follow option specified). The option –o follow must be specifically set when creating a backup task under the Options tab -> Additional call arguments -> Backup options (previously Save options) filed -> enter –o follow.
The integration of SEP sesam and Windows HSM solution is beneficial in terms of reducing your backup window by using HSM as a source-side data reduction system by migrating unused data to nearline storage, and SEP sesam as a target-side reduction system by using combined backup levels (full, differential and incremental) and data deduplication.