On Wed, Mar 29, 2000 at 12:28:01PM +0200, fooler wrote:
> Andi Kleen wrote:
>
> >
> > It has not been integrated, because equalization on the routing cache
> > layer does not work well (not fine grained enough or too slow)
> >
>
> hello andi,
>
> can you explain it further?
Linux has a routing cache that caches routing table lookups. This
is called the destination cache. A destination cache entry is tied
to a specific destination, which means only a single neighbour
on a multipath route. To use multipath routing for load balancing
requires dropping the destination entry after every use, so that
another neighbour in the multipath could be looked up (the destination
cache knows nothing about multipaths, that is all encapsulated in the
FIB or routing table)
Dropping them all the time does not work well and is slow. It is also
not finegrained enough (because the decision occurs to early) to get an
even load balancing
Multipath routing is only useful for failover when a device is down in Linux.
For load balancing you can use the existing eql, teql and bonding devices,
which work at a lower layer and avoid these problems.
-Andi
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This archive was generated by hypermail 2b29 : Fri Mar 31 2000 - 21:00:24 EST