On Fri, 2009-05-15 at 06:43 -0400, Lawrence Stewart wrote: > I'll echo the remarks about swapping, there is a large patch set for > swapping over IP, and we don't run that. In fact right now we run > without swap space, and vm_overcommit_ratio set to "90". This is > generous enough that we're not having problems, even on large > systems, > with running out of memory. Everyone seems to agree that having some > swap space is good for stability, so we do plan to add swap at some > point. We've got a new network block device that can swap over the > interconnect (without any allocations) at about 2 GB/s which is > probably > good enough to make DSM interesting. If you have local disks, using > them for swap will work fine.
Another problem which nobodys mentioned yet is where are you going to swap too? Sure each node might have 2GB/s network bandwidth to play with but no frontend is going to cope with more than a handful of nodes swapping at once. It might be viable for a network of diskless workstations but for a cluster forget it. The only way that network swapping can make sense in a cluster is if you know the application doesn't fit in memory and can allocate some extra nodes to host the swapped memory, preferably swapping over the network to RAM on a remote machine. This doubles the nodes required to run your job however and makes scheduling it with normal jobs impossible. Ashley Pittman, _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
