Hierarchical storage management

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A hierarchical storage management (abbreviated HSM ) is a system component that files , to which was not accessed for a long time, to a storage medium outsource that at a lower level of the memory hierarchy is, d. H. has a longer access time. Such a storage medium can be, for example, a magnetic tape or an optical storage medium . Slower storage media, also known as mass storage devices , are used here because they cost less with the same storage volume.

If a user tries to access such a file, the file is first copied from the slow storage medium to the faster storage medium. This process is known as recall .

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

HSM on z / OS

The method is used in particular in the mainframe area. For example, z / OS has a system component called the Hierarchical Storage Manager, or HSM for short , which operates such hierarchical storage management. HSM can also offload files on two migration levels. In the first stage, it saves the file in compressed form on an inexpensive hard drive ; in the second stage, it stores it on a magnetic tape or a virtual tape server . In addition, the time that HSM allows to swap a file can depend on certain parameters (management class, name, size, etc.) as specified by the system programmer .

HSM on Unix

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

The HSM implementation SAM-QFS is available for Solaris from Sun Microsystems , which provides an HSM system on a file system basis. It allows up to four media copies to be created in order to minimize the risk of data loss due to defective media.

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

The Grau Data company from Schwäbisch Gmünd offers the Grau Archive Manager, an HSM solution with archive function for Windows and Linux. The system is based on the respective native file systems ( NTFS or ext3 ). Grau Data has published an open source version of the GAM under the name OPENARCHIVE . This ensures that the data that has been archived remains legible forever.

Benefits of HSM

The use of HSM is worthwhile because it uses cheaper mass storage devices to store data stocks that are not needed over a longer period of time. The user hardly has to accept any loss of convenience here, since the data stocks are automatically restored when they are accessed.

literature

  • Ulf Troppens, Rainer Erkens, Wolfgang Müller: Storage networks . dpunkt, 2nd edition, Heidelberg 2008, ISBN 978-3-89864-393-1 .