Re: [squid-users] Why are we getting bad percentage of hits in Squid3.3 compared with Squid2.6 ?

From: Eliezer Croitoru <>
Date: Sun, 27 Oct 2013 18:58:45 +0200

Hey Manuel,

Squid 2.6 and 3.3.9 have couple changes that might cause this "side effect".
There is a big different from lower *hard* hits that being logged as
TCP_HIT to TCP_MISS/304 and many other combinations.

Analyzing squid access.log in 3.3 branch is not the same as 2.6\7\other.

If the origin server is serving an object that cannot be cached by
default troubles are probable to happen.
If the objects from the origin server are cachable by default then it
will be very simple to track down why the TCP_MEM_HIT or TCP_HIT has
lower rates.
Notice that TCP_MISS/304 can reflect a HIT that squid cache actually
made possible but the client software just verified that the object that
squid made possible to be cached was fetched from local cache(browser or
Squid has in the new branches a re-validation function that can seem
like not a HIT while it is an integrity check to make sure that the
client is fetching or fetched the right and up-to-date object from cache.
To make sure that 3.3.9 has high hit rate you will need more then just
You will need to understand how the logs and what the logs reflects.

If you want a more accurate verification get one copy of the
access.log(if there is one) and try to make sure you analyzed it in depth.
Can you find TCP_MISS/304 in the logs? if so how much of them?

If you need more help I'm here.


On 10/27/2013 06:43 PM, Manuel wrote:
> Hi,
> We are moving to new more powerful servers with CentOS 6 64bit instead of
> CentOS 5, with SSD instead of HDD and with Squid 3.3.9 instead of Squid
> 2.6.STABLE21. We are running Squid as a reverse proxy.
> The performance of Squid 3.3.9 seems to be excellent tested with around
> 125087 "clients accessing cache" and 20000 "file descriptors in use" in a
> single server but there is one big problem: we are getting much worst
> percentage of hits in Squid 2.6 in comparison with the same config in Squid
> 2.6. With the same config we are getting around 99% of hits in Squid 2.6 and
> just 55-60% of hits on Squid 3.3.9
> We are using the refresh_pattern options override-expire ignore-reload (as
> mentioned before is the same squid.conf config in every server -old and new
> ones-)
> Any idea on what might be the problem or any suggestion on how to find it?
> Thank you in advance
> PS: Since we have lots of concurrent connections requesting the same
> addresses we expect to add to the main webpages the Cache-Control
> stale-while-revalidate=60 header which I guess that will increase the number
> of hits on the servers running Squid 3.3.9 but for the moment the goal is to
> first try to reach a more similar percentage to Squid 2.6 in the same
> situation since stale-while-revalidate would be ignored by Squid 2.6.
> --
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> Sent from the Squid - Users mailing list archive at
Received on Sun Oct 27 2013 - 16:59:02 MDT

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