20050730: Linux: Benchmarking Filesystems In 2.6.0-test2

>From:  Gerry Creager N5JXS <address@hidden>
>Organization:  Texas A&M University -- AATLT
>Keywords:  200507301254.j6UCsDjo001244 Linux file systems inode

Hi Gerry,

Interesting read, thanks!  This was timely not only because of our
discussions -- several folks who attended the second LDM workshop were
also fighting Linux/RAID disk performance problems.  The worst example
of this kind of problem is when the LDM queue is on the same RAID as
the data being written.  One guy's setup was much like that on bigbird
-- dual Xeon (3.6 hz), 4 GB RAM, RAID.  His load averages and
performance mirrored what we have been seeing on bigbird.

>Found this interesting whiles trying to free up space on Bigbird last 
>evening.
>
>Tom, there is no mechanism in the current set of Linux kernels I can 
>find that allows modification of an inode to directly delete a directory 
>and all contents, although it's theoretically possible.

This is one of the first things I looked into before I wrote the
scourBY Tcl routines.  On some OSes (like Solaris), a delete is done by
simply manipulating the inode tables, so it is very fast.  For some
reason the Linux developers took a different approach.

>'rm' even with 
>the -rd switch, still wants the directories empty before removal.

Yup.

>May be worth looking at a new utility that enables inode write/directory 
>removal.

I agree.  The real question is why this does not already exist!?  One
would think that all of those folks that are benchmarking performance
on different file systems (ext3, riser4, xfs, jfs, etc.) would have dug
into the problem and presented a solution by now.

>http://kerneltrap.org/node/715

Cheers,

Tom
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