memcached "backends" (was Re: Simple questions from memcachednewbie)

[Jeetendra Mirchandani]

On Fri, 2006-10-13 at 17:58 +0200, Vincent van Leeuwen wrote:

> In this case you're trying to solve 2 seperate problems with 1 application:
> 1) compiling data into a useable form takes a lot of time
> 2) caching improves database performance
> 
> For 2) it's logical to use memcached, but 1) should be solved before 
> memcached.

I agree with you on this. 

The discussion started with me asking if someone has written a
redundancy layer for memcached. This makes sense as the data held by
memcached is important to me, even though my application(read database)
is capable of re-generating this cached data. I cannot tolerate a slow
performance because of a single memcached instance going down. If I have
the memory to throw at it, this redundancy is pretty straight forward to
achieve. 
Infact Jed has suggested a technique for implementing this redundancy in
a separate thread, though I have not gone through it in detail yet


> I personally see the academic value of multiple backends, but I don't see the
> practical value. It can only make memcached more complex (harder to maintain,
> more bugs) and probably also slower then it is now, so I'm against
> implementing such a thing.

About the persistent backend, almost everyone here uses some kind of a
database as a backend to memcached. And most of us don't really want a
relational database, but since it is the easiest, everyone goes that
way. So the discussion was that can we add an *optional* persistent
backend to memcached. 

Tugela was one alternative, but ideally I would want a backing store
behind memcached, and not replace the in-memory component by a backing
store.


> Memcached is a very specific tool for a very specific purpose, and should not 
> be used for purposes for which it isn't meant (at least not without realising 
> the implications).

I totally agree with you on this. Memcached is great, and one of the
most useful and easy software to use when it comes to caching!


-- 
Regards,
Jeetu

"The law of evolution is that the strongest survives!"