In today's world, HAMMER (file system) has become a topic of great importance and interest to a wide spectrum of people. From amateurs to experts, HAMMER (file system) has captured attention and generated debate in multiple areas of society. Its impact has transcended geographical and cultural barriers, being the object of study and analysis in different disciplines. In this article, we will explore various aspects related to HAMMER (file system), from its origin and evolution to its implications and possible future developments. Whether it is a historical phenomenon, a relevant figure or a current topic, HAMMER (file system) represents a meeting point for the exchange of ideas and knowledge, and it is necessary to understand it in its entirety to contextualize its relevance in our society.
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Developer(s) | Matthew Dillon |
---|---|
Full name | HAMMER |
Introduced | July 21, 2008DragonFly BSD 2.0 | with
Structures | |
Directory contents | Modified B+ tree |
Limits | |
Max volume size | 1 EiB |
Features | |
Forks | No |
File system permissions | UNIX permissions |
Transparent compression | Yes |
Data deduplication | On demand |
Other | |
Supported operating systems | DragonFly BSD |
HAMMER is a high-availability 64-bit file system developed by Matthew Dillon for DragonFly BSD using B+ trees. Its major features include infinite NFS-exportable snapshots, master–multislave operation, configurable history retention, fsckless-mount, and checksums to deal with data corruption. HAMMER also supports data block deduplication, meaning that identical data blocks will be stored only once on a file system. A successor, HAMMER2, was announced in 2011 and became the default in Dragonfly 5.2 (April 2018).
HAMMER file system provides configurable fine-grained and coarse-grained filesystem histories with online snapshots availability. Up to 65536 master (read–write) and slave (read-only) pseudo file systems (PFSs), with independent individual retention parameters and inode numbering, may be created for each file system; PFS may be mirrored to multiple slaves both locally or over network connection with near real-time performance. No file system checking is required on remount.
HAMMER supports volumes up to 1 EiB of storage capacity. File system supports CRC checksumming of data and metadata, online layout correction and data deduplication, and dynamic inodes allocation with an effectively unlimited number of inodes.
Currently,[when?] regular maintenance is required to keep the file system clean and regain space after file deletions. By default, a cron job performs the necessary actions on DragonFly BSD daily. HAMMER does not support multi-master configurations.
HAMMER is optimized to reduce the number of physical I/O operations to cover the most likely path, ensuring sequential access for optimal performance.
The following performance-related improvements were introduced in July 2011:
HAMMER was developed specifically for DragonFly BSD to provide a feature-rich yet better designed analogue[according to whom?] of the then increasingly popular ZFS.
HAMMER was declared production-ready with DragonFly 2.2 in 2009; in 2012, design-level work shifted onto HAMMER2, which was declared stable with DragonFly 5.2 in 2018.
As of 2019, HAMMER is now often referred to as HAMMER1 to avoid confusion with HAMMER2, although an official renaming has not happened. Both filesystems are independent of each other due to different on-disk formats, and continue to receive separate updates and improvements independently.