Smart File System: Difference between revisions

Revision as of 17:58, 20 December 2021

Revision as of 01:53, 15 July 2022

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== Features ==

SFS uses block sizes ranging from 512 (2⁹) to 32768 (2¹⁵) [[byte]]s with a maximum partition size of 128 GB.

Its good performance, better than [[Amiga Fast File System|FFS]], and lack of need for long "validation" in case of an error,<ref name="Hyperion">{{cite web|url=http://blog.hyperion-entertainment.biz/?p=210|title=Hard drive setup for AmigaOS 4.1 Classic|website=[[Hyperion Entertainment]] Blog|author=Darren Eveland}}</ref><ref name="TotalAmiga">{{cite journal|workjournal=Total Amiga|url=http://www.totalamiga.org/pdf/totalamiga_6.pdf|title=Hard Drivin'|page=45|author=Robert Williams|issue=6|year=2000}}</ref> is achieved by grouping multiple directory entries into a single block and by grouping meta data blocks together into clusters.<ref name="Forensics">{{cite book |author=EC-Council |title=Computer Forensics: Investigating Hard Disks, File and Operating Systems |date= 2009 |publisher=Cengage Learning |isbn=978-1-4354-8350-27 |pages=1–16 |chapter=Understanding File Systems and Hard Disks |url=http://news.asis.io/sites/default/files/Investigating_Hard_Disks_File__Operating_Systems.pdf }}</ref> A [[free space bitmap|bitmap]] is used to keep track of free space, and file data is kept track of using extents arranged into a [[B+ tree]] structure.<ref name="Forensics" />

Integrity is maintained by keeping a [[transaction log]] of all changes made to metadata over a certain period of time.<ref name="Forensics" /> The log is written to disk first into free space and then meta data blocks are overwritten directly. Should the system crash, the next time the filesystem is mounted it will notice the uncompleted operation and roll it back to the last known consistent state. For performance reasons, only metadata integrity is ensured. Actual data in files can still be corrupted if a write operation is terminated halfway through.<ref>{{cite web |url=http://www.amiga-stuff.com/text/filesystems/SFS.guide |author=Hendrikx, J |title=Smart Filesystem documentation |date=4 August 1998 |archive-url=https://web.archive.org/web/20040707174441/http://www.amiga-stuff.com/text/filesystems/SFS.guide |archive-date=2004-07-07 }}</ref> Unlike the original Amiga filesystems, [[Amiga Fast File System|FFS]] and [[Amiga Old File System|OFS]], filesystem integrity is very rarely compromised by this.