Ben Hathaway wrote:
Dear All,
I have recently set up a Squid cache using WCCP and a cisco router.
I am getting very impressive performance for my cache hits, but my cache
misses sometimes take as long as 4 seconds! We are at the end of a high
bandwidth, high latency satellite link with a normal latency (for example:
to google.com) of around 600ms round-trip. So why the 4 second delay?
Sometimes it comes down to 1.3sec but even that is a lot slower than I would
expect when my cache hits are being pumped out in 0.017s
Any ideas?
Here's my cachemanager stats (I've marked the relevant line with an
asterisk) :
Squid Object Cache: Version 2.5.STABLE9
Start Time: Thu, 15 Jun 2006 08:43:36 GMT
Current Time: Fri, 16 Jun 2006 07:14:09 GMT
SNIP
Median Service Times (seconds) 5 min 60 min:
HTTP Requests (All): 1.62803 1.71839
** Cache Misses: 3.11263 2.79397
Cache Hits: 0.01745 0.01745
Near Hits: 1.38447 1.24267
Not-Modified Replies: 0.01164 0.01164
DNS Lookups: 0.01535 0.02033
ICP Queries: 0.00000 0.00000
SNIP
Regards,
Ben Hathaway
For what it's worth, both your misses and Near Hits are double mine
(similar situation). Your DNS requests on the other hand are much lower
(my Squid server runs a caching DNS server as well, and DNS requests
show about 600ms). What is the output of "time wget -q -Y off -O
/dev/null http://www.google.com/intl/en/images/logo.gif";? This tells
wget to fetch the content quietly, without using a proxy, and to save
the file to /dev/null. Try it a few times to get a good sample set.
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).
Chris
![http://www.google.com/intl/en/images/logo.gif"](http://www.google.com/intl/en/images/logo.gif"){kind=link}