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SubjectRe: NTFS-like streams?


Alexander Viro wrote:
>
> On Sun, 13 Aug 2000, Jeff V. Merkey wrote:
>
> > Just remember, the real advantage NTFS in Windows 2000 garners from
> > these things is you can have an attribute with the same name attached to
> > each file. i.e. each file could have and ARCHIVE_DATA attribute
> > accessed as
> >
> > filename:ARCHIVE_DATA so a program can findnext all the files in a
> > directory and look for a specific piece of data it may have previously
> > associated with a file, so the naming system needs to be able to handle
> > instances of the same name across many files.
>
> Sigh... And then somebody sets "fascist" (read: reasonable) permissions
> and that program breaks. Right?
>

On Windows 2000, you can create an attribute with any name and as many
of them as you want. When you open the file, you access the attribute
file as filename:attribute and there is no logical limit to how many
differnt attributes a file can have chained from it. The typical use I
have seen in "real world" apps on NT that use this stuff is MS software,
like ExChange, SQL Server, an third party data mining apps. They
typically create their own "tag names" for the meta data unique to each
application, then just access them as files.
What's really nasty about trying to do this on a Unix filesystem is that
you could end up with lots of files with the same name associated with
different files, and need some way to keep them from colliding. Some of
the FS's would chew up a lot of dir space. In the real NTFS on W2K, the
names are emebedded in the MFT data record unless specifically defined
as external attributes, and even in this case, the attribute names are
not exposed via the MFT, which is a very nice mechanism on NTFS and
lowers overhead -- they're just LCN chains you traverse a lot like a FAT
chain on the DOS file system, but on Unix file systems, this could waste
a lot of dir space.
> Come on, guys, it's a feature from the Lisp Machines land. Single-user
> environment. Yep, having P-list stored with the object is handy, but it
> has _nothing_ to the things usually considered as filesystems. And it
> certainly doesn't work with multi-user systems. Linux is not Genera.

I must be too obtuse to understand this analogy.

:-)

Jeff

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