Custom File System for Linux

[Brian]

I have a production Solaris system that stores 4k chunks of text in really
big (2gig) files.

I have a new customer that would like access to the text as lots of 4k files,
that can be accessed with standard fopen, fread, fwrite.

Could a custom Linux filesystem be written that could map the big files into
virtual small files? I've read that writing filesystems for Solaris is not
documented, that's why Linux's open source approach is appealing.

If this is possible, could you tell me were to get started?

[Neil Matthew & Rick Stones]

Brian <aldie_lab@hotmail.com> wrote in message
news:395a93c6@news.devx.com...
>
> I have a production Solaris system that stores 4k chunks of text in really
> big (2gig) files.
>
> I have a new customer that would like access to the text as lots of 4k
files,
> that can be accessed with standard fopen, fread, fwrite.
>
> Could a custom Linux filesystem be written that could map the big files
into
> virtual small files? I've read that writing filesystems for Solaris is not
> documented, that's why Linux's open source approach is appealing.
>
> If this is possible, could you tell me were to get started?

Hi,

It is certainly possible to write your own file systems for Linux, the wide
range of file systems available are testament to that.

From the sound of it the features required for your production server are
fairly simple, it is not as if you are going to need to implement a
full-blown
general purpose file system.

To get started, take a look at the Filesystems HOWTO, you can get to it
here:

http://www.linuxdoc.org/HOWTO/Filesystems-HOWTO.html

Rather than delve into the depths of the kernel and write a complete
filesystem
from scratch, you should perhaps take a look at some other options. One that
might prove fruitful is userfs, a way to write filesystems in user space,
that
is ordinary processes can appear as file systems. You can catch up with the
latest developments of this approach here:

http://www.penguin.cz/~jim/userfs/

Currently Linux has a file size limit of 2Gb, so if you need to go bigger
than
this you may need to look at your own device driver and emulate a
filesystem.
One approach might be to replace fopen and fclose in the application
(perhaps
by preloading some of your own code in a shared object) and use a device
driver
to seek inside a raw disk partition to get to the 4K block you need.

Hope this helps
Neil and Rick