help a systems admin understand....

Brian Moon brianm at
Mon Dec 3 04:57:22 UTC 2007

> I'm assuming, since memcached has server tables? Then the issue of
> synchronization with memcached, all the databases at sites 2,3,4 will
> sync?

No.  Memcached is not a replicated cache.  It is a distributed cache. 
There is no syncing.

> The reason why I ask this, and I guess its maybe another question? Is
> that if a client goes to the load balancer, and the load balancer
> sends him to Site #2 the first connection, then after a few minutes,
> the client goes to Site #3 (because site #2 has high processes), the
> user will be able to access the same data? The concern is, if a user
> writes data to the database in Site #2, he won't be able to access the
> data again, if the load balancer redirects  him to Site #3.

That is an issue that is outside of memcached IMO.  memcached should 
only be used to speed up database operations.  If a user makes a change 
in site #2, it is up to your backends to sync that data to the other 
locations.  Memcached is a dumb, fast cache.

> Also, I suspect the php session gets lost because of the load
> balancer, which is why we install msession??

Again, that is application logic and not related to memcached except 
that memcached is a storage area for that data.


Brian Moon
Senior Developer
It's good to be cheap =)

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