Content etags are different when using many servers behind..

I have a problem. I have 5 IIS5.0 servers behind a load
balance switch. All servers have same content and answer to
one vip. I have a private proxy cache compiled from squid.
The problem I have is that the same objects from each
server have the same etags value except the last three
characters on the etag. Each server will generate a
different value of the three characters after the : in the
etags.

For instance one object will have an etag from one server
as such ( ETag: "259295695651c31:aaf" ). The same object
from another server will have an etag of such ( ETag:
"259295695651c31:b36" ).

As you can see the three characters after the ( are
different for each server. My private cache sees these as
different objects. Requests for the objects to my cache
will almost all the time require the cache to GET a new
copy from the Origin server because the client has a
different extention that it got from a previous request
that was handled by one of the other servers behind the
switch. Of course this is only happening when the clients
(browsers) version has expired, but is still fresh in the
private cache.

My question is how do I keep IIS from adding these three
characters on the etag after the ( so my cache hit rate
will be more efficient?

The ETag for a given object is based on the last modified timestamp on the
file, and a changenumber in the metabase...
It is not exposed, but you can get it at: mdutil get w3svc -prop 2039

By changing this metabase value to the same value on all web servers in
your server cluster, the same etag will be produced for the same objects on
seperate machines.

The following syntax is an example on what to set the value to : mdutil set
w3svc -prop 2039 -value "0x8037"

Thank you for choosing Microsoft
Miriam Green
Microsoft Developer Support

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