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Re: reverse proxy problem

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On 28/04/2012 9:38 a.m., Bruce Lysik wrote:
Hi guys,

Running latest 3.1 in a reverse proxy mode.  3 beefy servers with 96GB of ram.  Seeing an odd problem:

Origin ->  customer, equals fast speeds.  (Tested by curling from a desktop to origin.)
Origin ->  squid, equals fast speeds.  (Tested by running curl on the squid server to the origin.)
Squid cache hit ->  customer, equals fast speed.  (Seen in browser.)
Squid cache miss ->  customer, insanely slow.  36kB/sec, when origin to customer direct is like 50MB/sec.

Any ideas on what to look at here?  It's so broken it feels like a misconfiguration somewhere.

These are on RHEL6u2, 96GB ram, 1.69TB RAID5 ext4 partition for disk cache, 4gb of bonded network interface.  Machines are behind a load balancer operating in DSR mode.


The usual stuff is:

* disk I/O loading. Squid still cycles most objects through the disks when caching and RAID does horrible things to the write cycle speed.

* forwarding loops. If the traffic is looping in an dout and back again Squid impact can be huge.

* delay pools not being bypassed for the reverse-proxy traffic.

* QoS on the underlying system slowing things down.

* ECM or PMTU brokenness preventing the Squid box making fast jumbo-packet connections.



Amos


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