Smart File System: Difference between revisions

Revision as of 00:19, 14 October 2015

Revision as of 06:53, 14 October 2015

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== Features ==

Good performance of the filesystem, which is faster than [[Amiga Fast File System|FFS]] and doesn't require long "validation" in case of an error,<ref name="Hyperion">http://blog.hyperion-entertainment.biz/?p=210</ref><ref name="TotalAmiga">{{cite journal|work=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 realised 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=1-4354-8350-2 |page=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|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 half way through.<ref>Hendrikx, J: Smart Filesystem documentation. 1999</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.