Survey

[Richard M. Mathews]

fwp1 at CC.MsState.Edu (Frank Peters) writes:

>Well, we are developing a different kind of 'large system' that has
>its own unique complexities.

Good point -- large networks are also supposed to be part of this
newsgroup.  Actually, we have both kinds of "large" systems.  As I
said before, we have many AIX guests running on our 3090.  We also have
a handful of other 370s, each with a number of AIX guests.  Finally we
have many PS/2s running AIX.  Groups of these are connected via TCF,
and we use good old fashioned telnet, rlogin, NFS, etc. to connect the
clusters.

>(3)  Load balancing.  In a single box balancing the load among several
>     CPUs is relatively straitforward (at least in concept).  When
>     your CPUs are spread across a dozen or more machines how do you
>     avoid the situation of one machine being sunk to its knees while
>     another is nearly idle.  When you add multiple classes of
>     processor (is a 4/490 at 50% more loaded than a sparstation at
>     30%?) or multiple types  (how do the above two compare to a
>     decstation 3100 at 40%?) this issue can become a nightmare.

TCF allows processes to migrate between machines, and I know there are
others developing similar capabilities.  I can send a signal to a process
to request that it move to a new site (by default, to the site from which
the signal was sent).  A load leveling daemon could be written (but one
does not come with TCF) which automatically moves processes around in
response to varying load.  A difficulty is deciding which processes to
move -- it would be a shame to waste time moving an I/O bound process
which is currently accessing local data.  In our environment I have
found it quite sufficient to be able to manually move things when the
load goes up.

Richard M. Mathews
Locus Computing Corporation
richard at locus.com
lcc!richard at seas.ucla.edu
...!{uunet|ucla-se|turnkey}!lcc!richard