On 6 Nov 2000, at 6:03, Joe Cooper <joe@swelltech.com> wrote:
> > Imagine a setup: 10 caches, loadbalanced with L4 switch, seen as a
> > single cache by clients. Each box takes 1/10th of the http load, but
>
> I'm confused. Are there any L4 switches that don't provide a means to
> schedule cache usage based on a hashed value or some other network
> division to avoid redundant data? Even LVS now has a hash based
> scheduling algorithm so that there is never any redundant data on the
> balanced caches.
>
> ICP shouldn't come into the equation at all in an L4 balanced network,
> unless there are L4 switches that can't intelligently select a cache?
You are talking about transparent caching. If you have nontransparent
caching, then all those hashes can be thought of only inside proxy, or
based on URL, but then you'd need a L7 switch. You'd need to intercept
TCP session, wait and gather URL information (multi-packet, btw), and
then make decision on which cache to pick. This cannot be done fast in
hardware, so its not a job for a switch.
Besides, destination-based loadbalancing can easily overload a single
cache, so its not very optimal solution.
L4 balancing also implies dead-cache detection and redirection to other
caches. So, eventually destination IP based loadbalancing is not at all
attractive.
> ICP has some good uses, but use when balancing caches is unwise, I
> think.
ICP is all we have now. Digests seem better, but do not allow instant
knowledge of peer contents.
------------------------------------
Andres Kroonmaa <andre@online.ee>
Delfi Online
Tel: 6501 731, Fax: 6501 708
Pärnu mnt. 158, Tallinn,
11317 Estonia
Received on Mon Nov 06 2000 - 05:22:03 MST
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