Filesystems

See also: Computer

A set of data structures and methods for storing data on a physical disk.

Contents

• 1 Filesystems
• 2 Journaling Filesystems
  • 2.1 Ext3FS
  • 2.2 ReiserFS3
  • 2.3 XFS
• 3 Softupdates
• 4 Distributed Filesystems
• 5 Issues
• 6 Articles

Filesystems

• FAT12 – Used on floppies
• FAT16 – DOS, Windows “File Allocation Table” – a fast but error-prone filesystem
• FAT32 – Windows – 32-bit version of FAT, even faster
• NTFS – “NT File System” – Windows NT, Windows 2000
• HPFS – High Performance File System – OS/2
• UFS – Unix File System – various Unices, including Solaris and *BSD
• FFS – Fast File System – OpenBSD
• HFS – Hierarchial File System (also, HFS+) – MacOS
• Ext2 – Extended 2 filesystem – Linux
• VFS – Veritas File System – Veritas

Journaling Filesystems

A type of filesystem that keeps a journal (a log) of all writes to disk. When there is a non-physical disk crash, such as a power outage, the state of the disk can be corrected by replaying the transactions in the journal. This differs from non-journaling filesystems, where if there was data being modified during a crash, that data may very well become corrupt and unusable.

• Ext3 – Extended 3 filesystem – Linux
• ReiserFS3 – Journaling filesystem by Hans Reiser.
• ReiserFS – Modular journaling filesystem using dancing trees, among other features, by Hans Reiser. Aka ReiserFS4.
• XFS – for IRIX, Linux, by SGI
• JFS – another journaling filesystem, by IBM.
• NTFS – non-free journaling filesystem for Windows NT-family, by Microsoft
• VxFS – Veritas File System – Veritas

Ext3FS

• Extremely easy to transform Ext2 to Ext3 and backwards.
• Slower then both ReiserFS and XFS.

ReiserFS3

• Fast when reading small files.

XFS

• Fast when executing large binaries.

Softupdates

FFS and UFS, see Issues here under.

Distributed Filesystems

A type of filesystem that can be hosted across several fileservers while giving the appearance of being a single, unified filesystem, and which can be accessed from any one of several clients. Filesystems which incorporate some of these aspects include:

• NFS – Network File System
• SMB – Samba
• AFS – formerly, the Andrew File System. See now http://www.openafs.org <- ?
• Coda –

• For encrypting your link via a file systemn, see Encrypting-Your-Network-Links

Issues

• Fragmentation
• Metadata – A matter of ongoing debate is the desirability of including file metadata within the fileystem. An example of such metadata is the resource fork found in MacOS filesystems, which can hold information about the application which created the file. This makes some things easier, but at the expense of making the filesystem itself more complex (thus making other things more difficult).

• Journaling Versus Soft Updates: Asynchronous Meta-data Protection in File Systems

Articles

• Introduction to Linux filesystems and files. Includes information about various journaling filesystems.
• Optimizing Linux filesystems. A number of tips & tricks unleashed.
• Resizing and defragmenting Linux filesystems. Note that QTParted is a GUI frontend for GNU Parted.
• Recovering Linux files and filesystems. Again, also about journaling filesystems.

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