Regarding Memcached Server configuration?

Dustin Sallings dustin at
Thu Sep 27 03:34:31 UTC 2007

On Sep 26, 2007, at 10:39, Dan Christian wrote:

> Tell me if I understand this right.  If I run a memcached on each of 2
> machines, then the failure of a machine takes out half the cached
> objects.  These values will continue to be un-cached until that
> machine is removed from the client's configuration.

	Well, the client should recognize the brokenness of the server and  
avoid it.

> Is there an automatic recovery mechanism?

	An automatic recovery mechanism is generally undesirable.  If a  
server leaves your sight for a bit, the keys will be remapped to  
another server.  If it comes back, you'd remap back.  If it leaves  
again and you remap again, you're probably reading stale data.

	It's certainly possible to design around this.

> Is there a (big) performance hit when the configuration changes?

	Depends on how the configuration changes.  :)  If you've got a large  
cluster of memcached servers (presumably because you need a lot) with  
no consistent hashing and you change your client configs, you're  
going to suffer.  If you do the same thing, but with consistent  
caching and you add or remove a server, it'll be unlikely you notice.

Dustin Sallings

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