HAMMER

2014-07-25T23:07:42Z

Chrsschm: Spelling/grammar correction

{{For2|the Marvel Comics organization|[[H.A.M.M.E.R.|H.A.M.M.E.R]]}}
{{Infobox filesystem
| name = HAMMER
| developer = [[Matthew Dillon (computer scientist)|Matthew Dillon]]
| full_name = HAMMER
| introduction_date = July 21, 2008
| introduction_os = [[DragonFly BSD]] 2.0<ref name="phoronix" />
| partition_id =
| directory_struct = [[B+ tree]]<ref name="hammer-design-doc" />
| file_struct =
| bad_blocks_struct =
| max_file_size =
| max_files_no =
| max_filename_size =
| max_volume_size = {{nowrap|1 [[EiB]]}}<ref name="hammer-design-doc" />
| dates_recorded =
| date_range =
| date_resolution =
| forks_streams = no
| attributes =
| file_system_permissions = UNIX permissions
| compression =
| data_deduplication = on demand
| encryption =
| OS = [[DragonFly BSD]]
}}
'''HAMMER''' is a high-availability [[64-bit]] [[file system]] developed by [[Matthew Dillon (computer scientist)|Matthew Dillon]] for [[DragonFly BSD]] using [[B-tree]]s. Its major features include infinite NFS-exportable [[Snapshot (computer storage)|snapshots]], master-multislave operation, configurable history retention, fsckless-mount, and [[checksums]] to deal with [[data corruption]].<ref name="man-5-hammer" /> HAMMER also supports data block [[Data deduplication|deduplication]], meaning that identical data blocks will be stored only once on a file system.<ref name="dedup-devblog" />

A [[Porting|port]] of HAMMER to [[Linux]] has been started that supports read-only access.<ref name="hammer-linux" />

==Features==
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-filesystems (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.<ref name="man-5-hammer" /><ref name="descr-page" /><ref name="lwn" /><ref name="bsdmag" />

HAMMER supports volumes up to 1 [[EiB]] of storage capacity. File system supports [[Cyclic redundancy check|CRC]] checksumming of data and metadata, online layout correction and [[data deduplication]], and dynamic inodes allocation with effectively unlimited number of inodes.<ref name="descr-page" /><ref name="man-8-hammer" /><ref name="serverwatch" />

==Limitations==
Currently, regular maintenance is required for keeping file system clean and regaining space after file deletions. By default, a [[cron]] job is performing necessary actions on DragonFly BSD daily. HAMMER also does not support multi-master configurations yet.<ref name="descr-page" /><ref name="bsdmag" />

== Performance ==

The following performance-related improvements were introduced on {{dts|2011|7||}}:<ref name="ml-2011-07" />
* Increased disk read speed in certain scenarios by implementing pulse-width modulated time-domain multiplexer on B-Tree cursor operation
* Removed a deadlock stalling issue
* Improved read performance during heavy, concurrent file write operations

== {{Anchor|HAMMER2}}Development ==
It was developed specifically for DragonFly BSD to provide a feature-rich yet better designed analogue of then increasingly popular [[ZFS]].

{{As of|2014|6}}, ''HAMMER2'' file system is actively developed by Matthew Dillon, who initially planned to bring it up to minimal working state by July 2012 and ship the final version in 2013.<ref name="hammer2-design" /> During [[Google Summer of Code]]'2013 Daniel Flores implemented [[data compression|compression]] in HAMMER2 using [[LZ4 (compression algorithm)|LZ4]] and [[ZLIB]] algorithms.<ref name="gsoc-compression" /> On June 4, 2014 DragonFly 3.8.0 was released featuring support for HAMMER2, although file system was said to be not ready for use.<ref name="dfly38-release-notes" />

==See also==
{{Portal|Free software}}
* [[Comparison of file systems]]
* [[List of file systems]]
* [[btrfs]]
* [[OpenZFS]]

==References==
{{Reflist|30em|refs=

<ref name="bsdmag">{{cite journal |url=http://bsdmag.org/system/articles/attachment1s/15222/original/BSD_05_2014.pdf |title=Working with Hammer File System and PFSes |first=Siju |last=George |pages=18–23 |journal=[[BSD Magazine]] |volume=8 |issue=5 |publisher=Hakin9 Media SK |place=Warsaw, Poland |date=May 2014 |accessdate=2014-05-25}}</ref>

<ref name="dedup-devblog">{{cite web |url=http://www.shiningsilence.com/dbsdlog/2010/11/07/6740.html |title=Deduplication arrives |first=Justin |last=Sherrill |date=2010-11-07 |accessdate=2011-11-28 }}</ref>

<ref name="dfly38-release-notes">{{cite web |url=https://www.dragonflybsd.org/release38/ |title=DragonFly Release 3.8 |work=[[DragonFly BSD]] |date=2014-06-04 |accessdate=2014-06-05}}</ref>

<ref name="descr-page">{{cite web |url=http://www.dragonflybsd.org/hammer/ |title=HAMMER |work=[[DragonFly BSD]] |accessdate=2011-11-28 }}</ref>

<ref name="gsoc-compression">{{cite web |url=http://www.google-melange.com/gsoc/project/details/google/gsoc2013/iostream/5750892489867264 |title=Block compression feature in HAMMER2 |work=[[Google Summer of Code|GSoC]] 2013 |publisher=[[Google]] |accessdate=2014-06-05}}</ref>

<ref name="hammer-design-doc">{{cite web |url=http://www.dragonflybsd.org/hammer/hammer.pdf |title=THE HAMMER FILESYSTEM |first=Matthew |last=Dillon |authorlink=Matthew Dillon (computer scientist) |date=2008-06-21 |accessdate=2009-03-02 }}</ref>

<ref name="hammer-linux">{{cite web |url=http://dlorch.github.com/hammer-linux/ |title=Porting the HAMMER File System to Linux |first=Daniel |last=Lorch |accessdate=2011-11-28 }}</ref>

<ref name="hammer2-design">{{cite mailing list |url=http://leaf.dragonflybsd.org/mailarchive/users/2012-02/msg00020.html |title=DESIGN document for HAMMER2 (08-Feb-2012 update) |first=Matthew |last=Dillon |authorlink=Matthew Dillon (computer scientist) |mailinglist=users |date=2012-02-08 }}</ref>

<ref name="lwn">{{cite web |url=https://lwn.net/Articles/384200/ |title=DragonFly BSD 2.6: towards a free clustering operating system |first=Koen |last=Vervloesem |work=[[LWN.net]] |date=2010-04-21 |accessdate=2014-05-26}}</ref>

<ref name="man-5-hammer">{{man|5|hammer|DragonFly BSD}}</ref>

<ref name="man-8-hammer">{{man|8|hammer|DragonFly BSD}}</ref>

<ref name="ml-2011-07">{{cite mailing list |url=http://leaf.dragonflybsd.org/mailarchive/commits/2011-07/msg00086.html |title=git: HAMMER VFS - Add code to reduce frontend vs flusher locking conflicts |first=Matthew |last=Dillon |authorlink=Matthew Dillon (computer scientist) |mailinglist=commits |date=2011-07-22 }}</ref>

<ref name="phoronix">{{cite web |url=http://www.phoronix.com/scan.php?page=article&item=dragonfly_hammer&num=1 |title=Can DragonFlyBSD's HAMMER Compete With Btrfs, ZFS? |first=Michael |last=Larabel |work=[[Phoronix]] |date=2011-01-07 |accessdate=2014-05-26}}</ref>

<ref name="serverwatch">{{cite web |url=http://www.serverwatch.com/article.php/3763031 |title=Tip of the Trade: Dragonfly BSD and the Hammer Filesystem |first=Juliet |last=Kemp |work=ServerWatch |date=2008-08-04 |accessdate=2014-05-26}}</ref>

}}

== External links ==
* [http://www.dragonflybsd.org/hammer/ Hammer] on the official [[DragonFly BSD]] website

{{File systems}}

{{DEFAULTSORT:Hammer}}
[[Category:Distributed file systems]]
[[Category:2008 software]]

Wikipedia - Benutzerbeiträge [de]

HAMMER