remote operation or admin

Peter Jeremy peterjeremy at
Fri Mar 21 01:16:07 UTC 2008

On Wed, Mar 19, 2008 at 03:10:12PM -0400, Chuck Robey wrote:
>it might be possible to find some way to extend the work domain of an smp
>system to stretch across machine lines, to jump across motherboards.  Maybe
>not to be global (huge latencies scare me away), but what about just going
>3 feet, on a very high speed bus, like maybe a private pci bus?  Not what
>is, what could be?

This is definitely possible.  DEC built a memory channel adapter which
allowed multiple AlphaServers to share (part of) each other's RAM.  You
could also try looking at Amoeba - it is a cross between a "traditional"
SMP system and a cluster.  There's probably no reason why you couldn't
build a kernel module to "share" RAM between hosts using Ethernet or
similar - though it would be much slower than accessing local RAM.

>small, but with a bunch of bandwidth.  So, in that case, what really are
>the differences between smp and clustering, besides the raw current size of
>the implementation?   Are there huge basic differences between the
>clustering concept and by smp's actual tasks?

The access time differences between local and remote RAM mean that
there are different trade-offs: Memory coherence is extremely
expensive so more effort is expended in avoiding operations that
require coherence.  In general tasks that work well in a clustered
environment have very low inter-process communication requirements.

Peter Jeremy
Please excuse any delays as the result of my ISP's inability to implement
an MTA that is either RFC2821-compliant or matches their claimed behaviour.
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