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question about the dispersion ratio on Local Director

I have a question about the dispersion ratio on Local Director.

Network environment is as follows,

- one virtual server named "webapsv:80:0:tcp"

- two real server named "webap01:80:0:tcp" and "webap02:80:0:tcp"

two real server are always up, working

- "webap01:80:0:tcp" and "webap02:80:0:tcp" bind to "webapsv:80:0:tcp"

- predictor is roundrobin

- weight for each real server is 1

- persistence is made by cookie sticky and cookie is inserted by LD

with "sticky 192.168.2.131:80:0:tcp 300 cookie-insert LD-JRUNSV2"

The following are output of some show command

---------- show virtual ----------------------

Machines:

Machine Mode State Connect Sticky Predictor Slowstart

webapsv:80:0:tcp directed  local   IS 1 300   roundrobin* none

---------- show predictor ----------------------

Virtual Machine(s) Predictor Slowstart

webapsv:80:0:tcp roundrobin none

---------- show real ----------------------

Real Machines:

No Answer TCP Reset DataIn

Machine Connect State Thresh Reassigns Reassigns Conns

webap02:80:0:tcp 1 IS 8 0 0 1

webap01:80:0:tcp 0 IS 8 0 0 0

---------- show maxconns ----------------------

Real Machine(s) Limit

webap02:80:0:tcp unlimited

webap01:80:0:tcp unlimited

---------- show weight ----------------------

Real Machine(s) Weight Timeout

webap02:80:0:tcp 1 never

webap01:80:0:tcp 1 never

---------- show bind ----------------------

Virtual Machine(s) Real Machines/Urls

webapsv:80:0:tcp(IS)

webap01:80:0:tcp(IS)

webap02:80:0:tcp(IS)

---------- show sticky ----------------------

Virtual Machine(s) Sticky

webapsv:80:0:tcp 300 cookie-insert LD-JRUNSV2

In this environment, the traffic destined to the virtual server ("webapsv:80:0:tcp")

are not distributed to two real server (wabap01 and webap02) equally.

The following is the number of connections result of "show statistics" connections column

of the five days.

Real Server dispersion ratio

webap01 webap02 wabap01 : wabap02

Day 1 31692 21125 1 : 1.5

Day 2 57895 30381 1 : 1.9

Day 3 68370 51492 1 : 1.3

Day 4 85955 68221 1 : 1.3

Day 5 104666 84147 1 : 1.2

I do not why the dispersion ratio is not equally (1 : 1) between two real server even if

predictor is roundrobin and two real server are always up, working.

And why the dispersion ratio changes from high to low at every day.

In this environment, use cookie sticky and the cookie is inserted by LD (cookie-insert) and

the cookie expire timer is 300 minutes.

So I think the reason of

- the dispersion ratio is not equally (1 : 1)

- at every day the dispersion ratio approaches to equally (1 : 1)

are affected by the expire timer of cookie and this is the normal behavior.

My understanding is correct ?

Your information would be greatly appreciated.

Best regards,

2 REPLIES
Anonymous
N/A

Re: question about the dispersion ratio on Local Director

The slowstart option can be set using the roundrobin or none options of the predictor command. The roundrobin slowstart option load balances network connections until network traffic is stable. Refer URL for more information

http://cisco.com/en/US/products/hw/contnetw/ps1894/products_installation_guide_chapter09186a008007e9a2.html#xtocid2296014

Cisco Employee

Re: question about the dispersion ratio on Local Director

with stickyness you never get 1:1 ratio because a client stuck to server1 may open more connections than another client stuck to server2.

Gilles.

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