hesela.devHierarchical storage management
Hierarchical storage management automates data migration between storage tiers according to policies that balance access needs, capacity and cost.
HSM places less active data on lower-cost storage so higher-performance capacity can serve active work. Inactivity is a common policy input, not a requirement to use tape or any fixed sequence of media. [1]
File-based implementations can retain a local stub containing the information needed to locate and recall migrated data. Some metadata requests can be answered without fetching the payload. A pathname can therefore remain visible while its data is elsewhere. [2]
Premigration can retain the complete local file alongside its remote copy. In the documented client, later stubbing of premigrated files reclaims local space without resending their payload. A copied file is not necessarily a released file. [5]
Migration changes placement; it does not by itself establish an independently retained recovery copy. Back up resident and migrated files according to the recovery requirement. Restoring a stub and restoring the complete file are different operations: recall through a restored stub still depends on an available, matching migration copy. [4]
For recovery planning, check the namespace or stub metadata, backend payload and retrieval service together. Treat that as an engineering checklist, not a durability guarantee from an HSM label. [3] [4]
HSM need not use whole-file stubs. HighLight's 1993 design used a common block address space and fetched whole tertiary segments. Its initial selection policy still used file-level information; finer access-range tracking was future work. Distinguish the transfer unit from the policy's observation unit. [6]
Relations
- related
- Hot, warm, and cold storage tiers, Lustre HSM, Lustre HSM release, Cold archive tier, Backup, Restore test
Citations
- SNIA Dictionary: hierarchical storage management
- IBM Storage Protect for Space Management 8.2.0: Migrating files overview
- IBM Storage Protect for Space Management 8.2.1: Overview of the space management client
- IBM Storage Protect for Space Management 8.2.1: Backup and restore on space managed file systems
- IBM Storage Protect for Space Management 8.1.27: dsmmigrate
- Kohl, Stonebraker and Staelin (1993): HighLight: a file system for tertiary storage (author-uploaded full text)
Sources & caveats
- SNIA supplies the general concept; IBM manuals for 8.1.27, 8.2.0 and 8.2.1 supply implementation examples, not a universal stub format or recall mode.
- IBM documentation was read through indexed primary-source text; direct page requests returned HTTP 403. No HSM system or restore experiment was operated.
- The recovery-dependency checklist is an engineering inference. Human-facing context: https://hesela.com/analyses/snapshot-backup-recovery-boundaries/#hsm-placement
- HighLight's mechanism and policy sections were read in the author-uploaded full text. Publisher-linked DOI 10.1109/MASS.1993.289765 establishes 1993; the repository's 1996 label is not used as the publication year.