HSM definition by Webster's New World
hsm - Computer Definition
(1) (Hierarchical Storage Management) The automatic movement of files from hard disk to slower, less-expensive storage media. The typical hierarchy is from magnetic disk to optical disc to tape, or from magnetic disk to tape. HSM software constantly monitors hard disk capacity and moves data from one storage level to the next based on age, category and other criteria as specified by the network or system administrator. HSM often includes a system for routine backup as well. When a file is moved off the hard disk, it is replaced with a small stub file that indicates where the backup file is located. Tier 0 Storage Increasingly, solid state drives (SSDs) are used to hold data that are most frequently accessed and are a level higher than the hard disks. Consequently, data may migrate back and forth between the hard disk and SSD before being stored on optical and tape drives. See tape backup, active archiving, demigration and solid state drive.
(2) (Hardware Security Module) A device used to generate cryptographic key pairs, keep the private key secure and generate digital signatures. It is widely used to secure the root key in a PKI system. Using the PKCS#11 programming interface, applications send a digest of the document to the HSM, which encrypts it with the private key, creating the digital signature. HSMs can be very sophisticated in order to keep intruders from gaining access to the private key. See digital certificate and digital signature.