Re: [squid-users] Corrupt downloads via squid cache

OK, we now have the campus cache admin (Derek) on-board on this issue.
and he has provided answers to your questions, which I append, and
has asked me to progress the matter.

The configuration file is a sizeable document, so, rather than to
fling copies of it out to the whole list, I have stashed a copy here:

http://ppewww.ph.gla.ac.uk/~flavell/tests/campus-squid.conf

Derek adds the following remark:

| I'm not convinced there is a problem with Sun's memory management
|but if other sites using squid on non SUN platforms and with a
|similar load to ours are not reporting problems then there may be
|something in it. I use the dlmalloc library for speed rather than
|the SUN malloci.

----appended responses----

Hi Alan,

  Thanks for looking into this problem we all seem to have. I've been trying
to approach it systematically by changing one thing at a time but it won't go
away. I've attached a copy of the squid.conf file which we use on all off the
caches and provided answers to the questions Henrik raised. I also think this
is a genuine problem with the cache software or its configuration since all
the recent changes and upgrades I have made have failed to get rid off it.

Regards

Derek

INFO.

> a) What OS is the capus cache running on?

 The campus cache systems are thre SUN Ultra 5's with 270 MHz cpus and 512
MBytes memory each. Each system has 4 x 4 GByte ultras SCSI disks connected
with 2 each on separate controllers. Network interfaces are 100 Mbit/s.

The caches have a fairly high throughput with typically between 6 -7 Million
requests per day ( see figures below).

Figures for 8 May
*****************

Total Requests 6882692
Volume - Total Mbytes 42527.195
Peak Time 12:15 - 12:29
Peak Requests per hour 666315

Cache Performance

            No. % Kb/s std.dev
Hits 3380997 49.1 4.272 6.021
Direct 3226438 46.9 1.439 5.667
Error 275257 04.0

Figures for April 2002
**********************
Total Requests 149024734
Volume - Total Mbytes 1014860.656
Peak day 30 Apr
Peak Requests per day 7473809

Cache Performance

            No. % Kb/s std.dev
Hits 68685219 46.1 7.727 6.428
Direct 70527355 47.3 2.076 5.468
Error 9812160 06.6

> b) What Squid configure options has been used?

# ./configure --prefix=/usr/local/squid --enable-snmp --enable-async-io --enabl
e-storeio=diskd,ufs,aufs --enable-dlmalloc=./dlmalloc.o --enable-removal-policie
s=heap,lru

> c) What type of cache_dir is it using?

  The caches are currently using aufs for cache_dir. I tried using diskd on our
test cache for a while but it was fairly unstable.

cache_dir aufs /cache1 3500 16 256
cache_dir aufs /cache2 3500 16 256
cache_dir aufs /cache3 3500 16 256
cache_dir aufs /cache4 3500 16 256

Cache directories are mount using the noatime option.

> d) Which compiler was used to compile Squid?

 gcc version 2.95.1 19990816 (release)

> e) Do the campus cache use any peers?

  The three cache are configured as sibling off each other but do not peer with
any external caches.

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Received on Mon May 13 2002 - 05:22:37 MDT