Hierarchical storage management

Under a hierarchical storage management ( HSM short ) is defined as a system component that files to which have not been accessed for a long time, swapped to a storage medium, which is attributed to a lower memory hierarchy levels, ie, greater access time has. Such a storage medium may be, for example, a magnetic tape or an optical storage medium. The motivation of the use of slower storage media, also known as mass storage, justified by the lower cost per storage volume.

If a user attempts to access such a file, the file of the slow storage medium is copied back to the faster storage medium, this process is called Recall.

Hierarchical storage management is often used in combination with the electronic archive, document management, enterprise content management and data protection systems. A further development of hierarchical storage management is Information Lifecycle Management ( ILM), in which the information according to their value according to a set of rules will be moved to the most favorable storage medium.

HSM on z / OS

This method is especially used in the mainframe area. For example exists on z / OS, a system component that is called Hierarchical Storage Manager HSM short, and is responsible for a hierarchical storage management. HSM allows the definition of up to two migration steps for removing the files. In the first stage of migration, the file is compressed to a low-cost hard disk. In the second stage the file is stored on a magnetic tape or a Virtual Tape Server. In addition, the amount of time that must elapse before removal of a file, are defined by the system programmer on various parameters ( Management Class, name, size, etc).

HSM Unix

For Unix- AIX by IBM HSM is available as a Tivoli Storage Manager for Space Management for JFS2 and GPFS cluster file system. This product is also available for Linux ( with GPFS ), Solaris and HP- UX and is tightly integrated with the backup / archive product of the same TSM product family.

For Solaris from Sun Microsystems, the HSM implementation SAM - QFS is available, this is a HSM system to file system - based ready which allows you to create up to four media copies to the risk of loss of data due to defective media minimize.

For Linux, there SGI HSM DMF, which is sold commercially.

The company Grau Data from Schwäbisch Gmünd offers the Grey Archive Manager on a HSM solution with archive function for Windows and Linux. The system relies on the respective native file systems (NTFS or ext3). Grau Data has released an open source version of the GAM under the name OPEN ARCHIVES. In this way it is guaranteed that once the archived data forever remain legible.

Advantages of HSM

One advantage of HSM is the cost savings through the use of cheaper mass storage to store data files that are not needed over a long period of time. The user must accept this almost no loss of comfort, because the data sets is automatically restored when they are accessed.