Re: [Summary] Meta-data/filesystem-encapsulation

[Christopher Curtis <ccurtis ee fit edu>]

On Sat, 15 Aug 1998, Kevin Littlejohn wrote:

> So is gnome a linux-specific thing?  Or more correctly, an ext2-linux
> specific thing?  Can we put attributes on NFS-mounted files?  On MS drives?
> Am I allowed to use the metadata stuff, given I'm on Solaris (half the time,
> anyway :)?

You deleted the relevant portions of my post where I said that this was
the optimal solution, but we would still need a relatively reliable method
for those non-Linux/ext2fs users.

As far as NFS support, it actually falls into two categories as well:
Linux and non-Linux.  Linux would need a special NFS driver because files
written with this metadata would have it imbedded in the file - in front
of the real data if using the header method, or as a supplimentary block
if using the more wasteful method.  Linux NFS drivers should be able to
recognize a client requesting data with the "EA bit" set and send those
initial block(s) before the file as though it were ext2 itself.  If it's
missing this "EA bit", it would not get the metatype data, and would
resort to the fallback (aka non-optimal) method or forcing the client
program to figure it out for itself.  I'm not sure if there is spare space
in the ext2 inode for an EA block/bitmap, but you would have to agree that
this would be the optimal method.

Regardless, the problem remains even with this implemented.  (Though,
other filesystems can support it as well - like FAT could allocate an
extra block at the end of the file, etc, though this might get a little
funky for some data files depending on how they are setup.  The again, if
GNOME knows about these files, it should be able to write the extra data
in a non-(or minimally)disturbing way.)

> user.  Make it rely on things that mamy not be available to some users (like
> ext2 filesystems, or the ability to preload libraries across everything),

Well, as I said, it *need* not be ext2 specific - it can do multiple
filesytems to an extent, and will need a fallback method for heterogenious
environs anyway.  However, I don't know of many systems without PRELOAD
availablity (not that that's really relevant without a proper fs that can
be safely directly manipulated).

> and you reduce the functionality of gnome for parts of the userbase.

I never said anything that would reduce functionality.

> I still think the most important part of this system is not going to be
> where do we store the data, or how do we access the data - it's going to
> be how do we handle the data being desynchronised - because without
> redoing the filesystem (and loosing vast swaths of the userbase), we _are_
> going to run into synch problems.  How well the system recovers from those
> problems will be, to a large degree, the measure by which users judge the

Absolutely.  I think you'll find that there is no perfectly acceptable
answer.  So, with that in mind, why not have at least one such method
even if it does apply only to a limited userbase?  I'm sure that as GNOME
spreads outside of Linuxens other will find that they have similar ways to
modify Linux's fs drivers to implement these EA on native systems without
totally trashing their local fs's.

--
Christopher Curtis               - http://www.ee.fit.edu/users/ccurtis
                                 - System Administrator, Programmer
Melbourne, Florida  USA          - http://www.lp.org/