RE: [squid-users] 4 second Cache Miss Service Times

Dear All,

        Thanks for your suggestions. It seems there were some upstream
problems (resulting in packet loss) which we are trying to iron out with our
satellite communications provider. I still think there is something
suspicious about these service times, but I will have to wait a few days for
this other issue to be resolved before I investigate further. I'll post
again later when I have had a chance to try your suggestions.

        For Henrik & Chris who were concerned about DNS times - yes we have
a second DNS server sitting right next to the cache server. I made sure that
the DNS server had plenty of in-memory cache available so that it would
respond quickly to the second DNS request from SQUID. I thought that I could
disable the Squid DNS lookup completely if it proved too slow (if that is
possible?). At the moment this is not an issue.

        Michael - are you saying that I can expect service times of 3-4
Round-Trip-Time even in the best situations - something like 2 seconds? And
that this is simply the way that HTTP works (and therefore unavoidable)?
Apart from tinkering with TCP window sizes (which I will certainly look
into), is there anything else I can do to improve this?

Many thanks,

Ben.

-----Original Message-----
From: Henrik Nordstrom [mailto:henrik@henriknordstrom.net]
Sent: 18 June 2006 00:43
To: Chris Robertson
Cc: squid-users@squid-cache.org
Subject: Re: [squid-users] 4 second Cache Miss Service Times

fre 2006-06-16 klockan 12:43 -0800 skrev Chris Robertson:

> Perhaps the time required to make DNS queries is being included in the
> Cache Miss and Near Hits time due to using WCCP (my clients are set
> explicitly to use the proxy).

Yes DNS time is included in the service time. The service time is
measured from where Squid has read the request until it has finished
sending the response. But this does not exaplain the differences (see
below).

Squid always queries DNS for the host name, but only once/twice (it
caches the result internally).

When using WCCP the DNS service times should be a little better as the
client has just made the same DNS query and the result should be cached
in your central DNS, assuming both Squid and the client is using the
same DNS server (directly, or via DNS forwarder).

Regards
Henrik
Received on Sun Jun 18 2006 - 23:36:30 MDT