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Re: tar file system


From: Neal H Walfield
Subject: Re: tar file system
Date: Sat, 22 Dec 2001 01:13:03 +0100
User-agent: Gnus/5.090004 (Oort Gnus v0.04) Emacs/21.1

>> Basically what libraries, i need to use -- i think libdiskfs will be
>> needed!
>
> No, you should use libnetfs, because the nodes in the directory
> hierarchy provided by tarfs are "virtual" - in a way.

I disagree; libdiskfs should be used.

>From what I understand, libdiskfs is designed for the case where the
translator `owns' the backing store, e.g. ext2fs makes the assumption
that no one will modify the backing store while it is using it -- if
someone does, the protocol has been violated.  The same can be said
for tmpfs et al.

The libnetfs library, on the other hand, is designed for situations
where the implementation does not have complete control of the backing
store.  For instance, an nfs client must take into account that fact
that others can change the files on the back store (in this case, the
server) and that the copy it has might be out of date.  A proc-like
file system should also use libnetfs: the process data (pids et al) is
constantly changing.  In both of these cases, libnetfs makes the right
assumptions.

I think that the tarfs model is more similar to ext2fs than to nfs.

> - it could then for example build a complete hierarchy of nodes, which
>   corresponds to the content of the tar archive

Embracing the Unix philosophy, the implementation should be as lazy as
possible, i.e. it should wait until the very last minute to actually
fill in the data structures rather than doing all of the work on
startup.



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