mfs and buildworlds on the SunFire x4600

[Oliver Fromme]

Mars G. Miro wrote:
 > Oliver Fromme wrote:
 > > Mars G. Miro wrote:
 > > > there's been a lot of threads in teh past that a buildworld on mfs
 > > > increases speed --- tho it might not be the appropriate test for
 > > > high-end machines (speaking of w/c I just gots a T2000).
 > > 
 > > It depends on what exactly you want to test, and for
 > > what reason.  You probably have already wasted much
 > > more time with your experiments and testing than you
 > > can ever save by using mfs for buildworld.
 > 
 > wasted my time? dont think so.
 > 
 > now we know buildworld on mfs dont really matter on high-end machines,

No, we knew that before.  I could have told you.  :-)

That was the first thing I tested when I first had access
to a machine with sufficient RAM, about 10 years ago.
I put /usr/src on an MFS disk, ran buildworld, and was
disappointed.

 > so teh conclusion would be, buildworld isnt teh appropriate test if
 > mfs does really speed things up, other apps/tools may be much more
 > appropriate --- that or, does mfs speeding things up really work?
 > remains to be seen ...

The only case for which a memory file system is really
faster is when you're handling a huge number of inodes,
for example the ports collection.  And even then a real
disk isn't much slower as soon as the whole bunch is in
the cache.

 > > > there's prolly other appropriate apps/tools for mfs-testing ...
 > > 
 > > I don't think it makes much sense to benchmark mfs.
 > > It is a known fact that a real tmpfs (like Solaris and
 > > Linux have) would be better.  I think it's even listed
 > > on the FreeBSD ideas web page, but nobody is actively
 > > working on it, AFAIK.  On the other hand, I'm not 100%
 > > convinced that it would be worth the effort either.
 > > 
 > 
 > it does to me, however, and perhaps other people too ;-)

Why?  I wonder why you are so eager to test MFS?

 > > It would be interesting to see how ZFS on a swap-backed
 > > vnode device would perform on FreeBSD 7-current (with
 > > and without compression).

You didn't comment on that one.  Aren't you interested in
how a ZFS-based memory disk would perform, as opposed to
a UFS-based one (a.k.a. "MFS")?

(Of course, performance isn't everything.  ZFS has other
features such as compression, checksums and dynamic growth
that might be very useful for a memory disk.)

Best regards
   Oliver

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