Filesystems

Albert Cahalan (albert@ccs.neu.edu)
Sat, 16 Mar 1996 01:48:33 -0500 (EST)


>>> and the authors are looking at alternatives to sync writes which
>>> preserve the metadata consistency (by using either ordered async
>>> writes or rollback mechanisms).
>
>> I'm under the impression some of the USL related people have
>> a US software patent on ordered async writes. Probably worth
>> someone checking this out.
>
> Yes. Novell obtained such a patent for Unixware. Terry Lambert was
> working for them at the time and can supply all the unpleasant
> details. Fortunately, Ganger's soft update mechanism is based on
> rollbacks, not ordered writes, so is not affected by the patent. Soft
> updates are probably the way to go; they don't suffer from the
> horrible cyclic dependencies of ordered write implementations.

OK, why not then? :-)

I would imagine that both rollbacks and ordered writes would mean
severe changes to the VFS layer, right? Might as well add the
ability to resize a live filesystem too.

I've heard that ext2 directories are a bit slow,
and should use B-tree structures like HPFS or NTFS.

Dynamic inode tables would be nice.

BTW, secure delete needs to be fixed, and fsck should know
what to do with lost inodes that are marked for secure deletion.