Re: Linux filesystems

[Steven Pritchard <steve@silug.org>]

On Wed, Mar 24, 2004 at 10:44:19AM -0600, Roger_Hill@May-Co.com wrote:
> Which type of filesystems are better ? Windows NTFS or Linux's ?

As I understand it, NTFS is a log-structured filesystem.  (Like many
things in NT, that kind of filesystem was the Big Thing to CS
professors at the time it was designed.)  For a description of what
that means, see here:

  http://en.wikipedia.org/wiki/Log_structured_filesystem

There's also a fairly detailed description of NTFS specifically here:

  http://en.wikipedia.org/wiki/NTFS

(I'm getting sucked into Wikipedia now...)

This page says NTFS is a journalling filesystem:

  http://en.wikipedia.org/wiki/Journaling_file_system

So I'm going to stop looking at all this and leave the real answer as
an exercise for the reader (and Google).

Anyway, back to log-structured filesystes for a moment...  There have
been a couple of these for Linux at one point or another, such as
this:

  http://www.complang.tuwien.ac.at/czezatke/lfs.html

(Like I said, it's a big thing for CS people.)

So, switching gears, "better" is more than a little subjective, even
ignoring Windows-vs-Linux, so I'm just going to focus on Linux
filesystems.  The "default" filesystem on Linux is ext2/ext3 is
relatively primitive by today's (CS :) standards, but it was designed
to be extended, so it has been slowly incorporating features of more
advanced filesystems over time.  It is certainly not a bad filesystem,
and it has the distinct advantage of having a *huge* installed base
and an *insane* amount of testing for the filesystem itself and the
tools.

The truely advanced filesystems available for Linux are XFS and, to a
lesser extent, JFS.  As I understand it, both support on-line resizing
out of the box, as well as a lot of other nifty stuff.  Of course,
both have the advantage of having a long (previous) life on other
operating systems (IRIX in the case of XFS, and both AIX and OS/2 in
the case of JFS).  Of the two, XFS almost certainly has the least
legacy cruft.

Theoretically reiserfs is up there with XFS and JFS, but in practice
it appears to be a bit unreliable.  That may just be a function of the
tools, which have probably had a lot less testing than those for any
of the other mainstream filesystems.

> Someone (a Windows NT person) stated that NTFS is a much more
> secure file system, has more control (ACL's) I thought Linux also
> had an ACL function for it's filesystems.

I think every Linux filesystem has some kind of ACL support, but
there's a school of thought that the simpler security provided by
standard Unix filesystem permissions tend to give much better security
given that they are easier to understand and easier to verify.

The real security problem with NTFS isn't the filesystem itself
though...  The real problem is that M$ ships every version of Windows
with "full control" enabled for "all" on every filesystem, including
the one where Windows itself is installed.  The only thing that even
begins to save Windows is that files that are actively in use by the
operating system can't be changed.  (Of course, that can be easily
circumvented by adding things to the registry, modifying things that
are only used on boot-up, etc.)  And to top it all off, if an
administrator decides to lock down a Windows box, things are likely to
break in big ways since most Windows apps (including ones from M$)
have *no* understanding of how to work with filesystem-level security
enabled in any way.

In other words, NTFS could be the most advanced filesystem ever, and
it wouldn't help Windows security one bit.

Steve
-- 
steve@silug.org           | Southern Illinois Linux Users Group
(618)398-7360             | See web site for meeting details.
Steven Pritchard          | http://www.silug.org/

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