Slow responses

I have a squid 1.1.18 running on a DEC alphaserver 800 box, with
DEC unix 4.0b. The cache filesystem is 16GB.

When the cache gets a lot of requests (it serves over 2 million requests
each day, and at peak reaches nearly 50 requests per second) the response is
horrible. Pages that can be fetced directly from the webserver
may take a minute or two from the cache. There is no paging going on, and
neither raw disk I/O nor network I/O seems to be a problem. Of my 16 dnsserver
processes the last few are rarely used. CPU load rarely goes above 0.5.

The only oddity I find is this line in cache.log, appearing every few seconds
while the cache is busy.:

98/01/22 23:09:52| diskHandleWrite: FD 23: disk write error: (32) Broken pipe

Is this related? Any idea what might be the problem?

-- 
Terje Krogdahl
Telenor Nextel AS