On Fri, Oct 12, 2012 at 11:31 AM, Kiran Kumar <krn1...@gmail.com> wrote:
>
> Thanks LesMikesell you were right there is nothing mentioned anything
> about data being backed up in that link .
> What i really want to convery is that if one of the Memcahe Server one is
> is down , then automatically Data is being obtained from Memcahe Server two
> , which avoids single point of failure . so i don't care if Data is being
> obtained from any of the defined servers .
>
> ( that is what i mean to say data being copied to other location , i
> sincerely if it creates a different meaning in this context )
>
> (becuase as a end user i don't bother from which the data is being
> obtained )
Memcache should only be used for fast repeated access to _copies_ of
data that can be reliably retrieved from some other database or
storage. There are any number of reasons why a server will not have
the data a client requests (it expired, it was evicted due to lack of
space, the server was restarted, etc.). The client's response to a
cache miss should always be to get the data from the reliable database
and update it into the cache. So it won't matter if any particular
data is lost for any particular reason as long as the backend database
can keep up with the clients requesting the missed data (which they
will then refresh into a rebalanced hash location). If you are
planning to use memcache to store the only copy of data that you can't
reconstruct, you should be looking for some other product. Memcache
is just a very fast distributed cache, not a reliable database. But
as long as you can retrieve the data for cache misses from some other
source you can just add more servers to a cluster to scale to any
size, and other than having to configure each client to know about all
the servers it will take care of itself.
--
Les Mikesell
lesmikes...@gmail.com
