Dynamic Storage Acquisition with Minimal Fragmentation in Disk-Disk Backup/Archival Environment
Original Publication Date: 2004-Nov-10
Included in the Prior Art Database: 2004-Nov-10
Tivoli Storage Manager has made enhancements to facilitate all-disk backup solutions. The disclosed invention ensures that sufficient disk space is available on-demand for backup and archival operations, without requiring pre-allocation of large amounts of space in advance. An additional advantage is that space fragmentation is limited.
Dynamic Storage Acquisition with Minimal Fragmentation in Disk -Disk Backup/Archival Environment
For more than ten years, Tivoli Storage Manager has supported disk storage pools -- groupings of storage volumes based on disk files. Disk storage pools can be configured in one of two modes, random access or sequential access, each with its own advantages. In Tivoli Storage Manager parlance, each random access or sequential access file is called a volume. Random access disk storage traditionally required pre-allocation of space, while sequential access volumes were normally acquired dynamically. Sequential access files were created and deleted on an as-needed basis, but space was typically acquired as needed when the volume was in use. The disadvantages to sequential access volumes were the potential for file system fragmentation and the performance drawbacks of dynamic file size expansion while in use. The problem with creating volumes with enough space for future use at acquisition time is the inherent delay in reserving the space through the file system and preparing it for use by the backup/archival system.
In dealing with large requirements for disk space in a backup/archive solution, it is desirable to delay allocation of space until it is actually needed, and to acquire space in contiguous blocks with minimal fragmentation to improve performance. Current solutions acquire space from the file system at file write time, which does not guarantee that the space can be acquired (if other processes have acquired the space already). In a highly multiplexed environment, there is also a high probability of acquiring space in discontiguous segments.
Description of the Invention
Disclosed is an implementation of a space trigger mechanism in which the utilization of space is monitored in each disk storage pool. Using predefined thresholds based on space utilization of the entire storage pool, additional space is dynamically acquired. Space is acquired in a manner that minimizes fragmentation and is acquired when the need for the storage is imminent. Utilization statistics are based on Tivoli Storage Manager's use of the storage already in its hierarchy; triggers may be defined as a default for all storage pools without specific triggers, or on a storage-pool-specific basis. The amount of space to be acq...