Re: [lvs-users] different algorithms and persistence

To: " users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] different algorithms and persistence
From: Nikolaj <lorddoskias@xxxxxxxxx>
Date: Fri, 26 Oct 2007 15:33:05 +0300
Joseph Mack NA3T wrote:
> On Fri, 26 Oct 2007, Nikolaj wrote:
>> If I'm right about the hashing as I said above, what's the difference
>> with source hashing?
> what's the difference between source hashing and what?
The difference between source hashing and round-robin. If someone makes 
a connection and with round robin is redirected to realserve1 (for 
example) won't the subsequent connections to the same service go to the 
same realserver1? Because when a connection is made (irrespective of the 
used algo) LVS hashes the attributes of that connection - IPs, sequence 
numbers etc?

>> For example if a given ip has already made a
>> connection to one service and made another connection to a different
>> service but with the same source ip address the second connection will
>> be redirected to the same real server as the first one, won't it?
> if the client makes a 2nd connection to the same virtual 
> service at some later time, the connection will go to the 
> same realserver.
>> Excerpt from the howto
>> "The -dh (destination hash) algorythm makes a hash from the target IP
>> and all requests to that IP will be sent to the same realserver. This
>> means that content from a URL will not be retrieved multiple times from
>> the remote server. The realservers (eg squids in this case) will each be
>> retreiving content from different URLs."
>> But the client doesn't know what are the real ips of the real servers
>> how can they be cached (the ip addresses)? Or maybe LVS hashes the
>> destination ip after it receives the packets and decides to witch real
>> server to send it?
> -DH is for squids. The target address is the IP of the URL, 
> not the VIP or the RIP
Hmz, I'm baffled. For example if I want to retrieve 
(random ip address) isn't it necessary to have this ip as VIP bound on a 
LVS redirector? If you could elaborate on this, please.

>> I'm ready to write it, as soon as I'm confident with the differences
>> between the different scheduling algorithms and the pros and cons.
> great
> Joe

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