Is memcached a good way to store session share ammong web servers?

[NTPT]

Failover and fault tolerance in memcache ? 

What about something like "software RAID" ?

ie memcached server is as a "disk" and client application that provide RAID like functionality ? you can put several "disks" ie memcached servers to system , with on top of the memchached servers sitting an application that behave analogically to RAID 5 array ? = failover and redundancy ? and even a hot swap .o) 

Please execuse my wrong english

>  ------------ Původní zpráva ------------
>  Od: NTPT <NTPT at seznam.cz>
>  Předmět: Re: Is memcached a good way to store session share ammong web servers?
>  Datum: 13.11.2006 22:14:07
>  ----------------------------------------
>  Failover and fault tolerance in memcache ? 
>  
>  What about something like "software  RAID"  ?
>  
>  ie memcached server is  as a  "disk" and client application  that provide RAID
>  like functionality ?  you can put several "disks" ie memcached servers  to
>  system , with on top of the memchached servers  sitting an application that
>  behave analogically to RAID 5 array  ? = failover and redundancy ?  and even a
>  hot swap .o) 
>  
>  Please execuse my wrong english
>  
>   
>  
>  >  ------------ Původní zpráva ------------
>  >  Od: Perrin Harkins <perrin at elem.com>
>  >  Předmět: Re: Is memcached a good way to store session share ammong web
>  servers?
>  >  Datum: 13.11.2006 16:12:55
>  >  ----------------------------------------
>  >  Peter Bengtson wrote:
>  >  > True, 
>  >  > if someone were to switch off the box running the sessions memcache 
>  >  > store, users would be logged out and would have to log in again. But you 
>  >  > can get around that by using several memcache instances.
>  >  
>  >  I don't think that will help.  It's not replicated, so if you run two 
>  >  memcached serves and one goes down (or segfaults, or runs out of memory) 
>  >  you lose half your data.  Better than losing all of it, but not for the 
>  >  people whose sessions just disappeared.
>  >  
>  >  > Also, the same 
>  >  > problem applies to any solution: if your session storage disks become 
>  >  > full, for instance, or if your load balancer suddenly crashed. There 
>  >  > will always be vulnerable spots.
>  >  
>  >  There are tools you can use which provide redundancy and failover for 
>  >  stored data.  You can't get that from memcached at this point.
>  >  
>  >  You can also just use memcached as a cache, and keep the permanent 
>  >  storage in something more durable.  That works great for read-mostly data.
>  >  
>  >  - Perrin
>  >  
>  >  
>  >  
>  
>