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I'm working my way down the stack but haven't yet learned about filesystems. When comparing filesystems, what are the main attributes I can expect to encounter in my research?

The Wikipedia topic is... a bit daunting. If I want to focus on the "palpable" attributes of a modern filesystem (journaling, blocks, chunks etc.), what are the main attributes on which to focus?

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migrated from serverfault.com Jan 5 '11 at 9:45

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The only interesting parts (in finding out the main attributes of file systems) of that web page are the titles of the Features and * Allocation and layout policies* tables, and the fact that there is a Metadata section. –  Daniel Beck Jan 5 '11 at 9:48

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up vote 5 down vote accepted

The most important attribute is likely to be

  • Reliability

because you want the data to be safely written and retrieved at anytime.
Usually it takes years to have a FS tried and tested.
Integrity leads to dependencies. For instance, in special occasions, like power cut or system crash,

  • Data integrity

is a crucial factor. Journaling is commonly an attribute that maximizes data integrity.

  • Speed

is also important. Journaling is likely to slow down write operations.
Speed depends also upon the implementation of the FS, using of memory, caches...

  • Systems versatility

Is the FS readable from another operating system? For instance, it works on Linux, but can you mount and read it from Mac OS?

Other attributes may or may not an important factor, depending on your needs

  • Encryption: does the FS handle data encryption, requiring a key to mount it?
  • Read-only: an attribute to allow a write-protected mount
  • relatime like attribute, allow to write the access time only during write operations (to minimize the TOC writings)

For instance, some explanations of the ext4 file system mount options.

Edit - about the Access Control List (per-user / group access to the data)

The ACL is not really an attribute of the FS.
It can be integrated within the file system, but, depending on the FS, mounting from a platform to a different platform may completely override the user access control. The global access being controlled by lower level attributes. as the ones detailed above for instance.

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Thank you for this excellent answer –  editor Jan 5 '11 at 5:27
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You've missed security: the ability to define who can perform different types of access to different objects in the file system. –  Richard Jan 5 '11 at 10:36
    
@Richard See my edit –  ring0 Jan 5 '11 at 11:05
    
@ring0: I don't follow your logic. Security can be bypassed on most OSs by the "root" user, this doesn't mean the file system's security is irrelevant (especially where many users make use of the file system). –  Richard Jan 5 '11 at 12:03
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@Richard, File security is just metadata that the OS interprets and enforces. The File System does not enforce security. Root can only override security because of how it interacts with the kernel; the file system on disk couldn't care less about root. –  Chris S Jan 5 '11 at 13:47

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