Regarding Memcached Server configuration?

[BUSTARRET, Jean-francois]

I can think of two cases where multiple instances of memcached on the same server are useful :
1/ to be able to use multiple processors without using the threaded version of memcached (but IMHO, using a single/multi-threaded version should be better)
2/ to be able to store datatypes with incompatible lifetime/storage policies or with specific flushing policies. ie :
- isolating a session cache from a data cache : you might not want new sessions to kick off important (complex to generate but accessed not very often) data, or having too many slabs for sessions when they could be of better use for data (if your data is not of the same size than your sessions)
- being able to flush all of datatype A without touching datatype B (you can't flush half of your cache, but you can flushall instance A without touching instance B).
 
Otherwise, IMHO, having a single instance with a lot of memory makes more sense (or better, two instances on two different servers, each with a lot of memory)
 
Jean-François


________________________________

	De : memcached-bounces at lists.danga.com [mailto:memcached-bounces at lists.danga.com] De la part de Ajinkya Nahar
	Envoyé : mercredi 26 septembre 2007 11:57
	À : 'Marcus Bointon'
	Cc : memcached at lists.danga.com; 'Nishith Shah'; 'Sunil'
	Objet : RE: Regarding Memcached Server configuration?
	
	

	Hi,

	 

	I will be configuring memcached on a different server altogether.

	My query was regarding how much memory to allocate and how do I setup the memcached instances on that server.

	 

	Thanks,

	Ajinkya

	
________________________________


	From: Marcus Bointon [mailto:marcus at synchromedia.co.uk] 
	Sent: Wednesday, September 26, 2007 2:44 PM
	To: Ajinkya Nahar
	Cc: memcached at lists.danga.com; 'Nishith Shah'; 'Sunil'
	Subject: Re: Regarding Memcached Server configuration?

	 

	On 26 Sep 2007, at 07:04, Ajinkya Nahar wrote:

	
	
	

	I am working on a PHP - Mysql based web application.

	 

	I am using memcached for caching purpose.

	 

	I have one query regarding memcached server setup as follows -

	 

	If we have 1.7 GB memory on a server, how much should we allocate to memcached assuming there is nothing else running on the server.

	 

	Also, if we decide to allocate 1.5 GB, in that case, is it good to have just 1 memcached instance running or let's say 3 - each with 0.5 GB?

	 

	We are using the latest PHP memcache client which implements consistent hashing strategy.

	 

	If you are only running one server, you might be better off using APC for your caching. If you have 2 servers, you might get better performance by running your PHP on both, and also using both for memcache (with memcache the more physical servers you have, the faster it can go, on average). This will also give you a bit of redundancy, letting your service continue if one server dies.

	 

	Marcus

	

	-- 

	Marcus Bointon

	Synchromedia Limited: Creators of http://www.smartmessages.net/

	UK resellers of info at hand CRM solutions

	marcus at synchromedia.co.uk | http://www.synchromedia.co.uk/

	
	
	

	 

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