On Thu, 15 Nov 2001, Henrik [iso-8859-15] Nordström wrote:
> While trying to figure out how to best make use of the WebAxe-4
> workload in testing I came across the following small questions:
>
> a) What does the requested server names look like. I assume the IP
> addresses of the servers are used, but this makes it impossible to
> use any load backend load balancing selections in the surrogate
> and somewhat complicates the mapping of requested URL's to real
> web servers..
Clients think that the requests are directed to a single "origin"
server. That server is represented by a surrogate (a.k.a., reverse
proxy or Web accelerator). The surrogate distributes the load among
several true origin servers. Those origin servers are assumed to be
identical as far as content is concerned.
You can configure Polygraph to test multiple different origin servers,
accelerated by a single cache, but that would not be a WebAxe
workload.
> b) How static is the URL namespace used? Is the same working set
> of URLs used for the whole duration of the test, or is there
> variance in the URL namespace?
Working set "slides". The changes in working set are slow due to very
high recurrence ratio of WebAxe. The set slides with the rate the new
objects need to be introduced based on recurrence ratio.
The size of the working set remains constant and is configurable.
> c) I read that the test used a 1GB set of origin data. Does the
> "cache size" have any relation to the test at all?
Not from Polygraph point of view. Most surrogates will have at least
working set size of storage and probably more.
> Found the answer to the question on cache size (none, except for
> the fill phase)
The fill phase is not affected by the cache size for this test. You
may be thinking of PolyMix where the duration of the fill is
determined, in part, by the cache size.
It is a good idea to fill the cache first though. We just wanted to
shorten WebAxe tests because we do not expect performance to depend
much on the disk subsystem (as opposed to PolyMix). Most reasonable
surrogate configurations will cache the majority of WebAxe objects in
RAM.
> But instead I now have another question. In the workload
> description it says that there needs to be at least 4 servers.
> Does this mean that the minimum webaxe4 test bench is 5 polygraph
> machines? (1 client, 4 servers).
You can run 4 server agents inside one polysrv process if needed. Just
make sure your server host is not overloaded.
> Why is this requirement on at least four servers?
Two reasons: many surrogates accelerate more than one physical server
and to make sure the surrogate has an option of balancing the load
across multiple servers.
If your environment is different, and you are running private tests,
you may want to violate this rule and use just one server.
Alex.
This archive was generated by hypermail 2b29 : Mon Feb 06 2006 - 12:00:20 MST