help a systems admin understand....
brianm at dealnews.com
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
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.
It's good to be cheap =)
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