Re: Ken Thompson interview in IEEE Computer magazine (fwd)

Ian D Romanick (idr@cs.pdx.edu)
Fri, 7 May 1999 11:47:51 -0700 (PDT)

> > > That's why most `SAN' solutions are at a higher level. Life is much
> > > easier that way, and you may not lose many of the advantages of
> > > clustering.
> >
> > Life might be easier, but you end up imposing artificial limitations on
> > the usage of available bandwidth by serializing the data path.
>
> That depends on whether your cluster filesystem is parallel or
> not. Most existing SANs (based on SMB/CIFS) aren't parallel, but you
> can build a parallel filesystem on top of one. That's what Legion
> does.

What exactly do you mean by parallel? There's pretty much two clean ways to
do it. One system has access to the physical disks that hold the filesystem
or multiple systems have direct access to the physical disks. NFS/SMB/Coda
use the former. Sequent's CFS and the similar product for
Digital/Sun/HP/IBM use the latter. In the former you are limited by the
performace of the system that has access to the disks. In the latter you
are limited only by the speed of the disks and the interconnect (to the
disks). I can tell you without even thinking too hard which is faster. :)

-- 
"Bob's Constant: the number of beers required for Bob to
 think that ANY woman is beautiful."


                                                  http://www.cs.pdx.edu/~idr


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