[geeks] sun ultra 24

[Sridhar Ayengar]

Lionel Peterson wrote:
>> FB-DIMMs do have some advantages (latency not being one of them,
>> and their performance issues are largely masked by the massive
>> on-chip L2 caches that Intel uses as well as a lot of extra work
>> they put into their memory controllers).  FB-DIMMs can be set up to
>> have failover modules so in a situation where a module goes bad in
>> use, the motherboard can stop using it and switch to it's mirrored
>> module (similar to RAID) without missing a beat.
> 
> What the heck??? Any pointers to info on such an arrangement (even if
> only in theory)? I don't see how it would work, as when the module
> fails, it will take a gig of data with it (how does the "hot spre"
> RAM module get populated once an error is detected?).
> 
> Oh wait, you mean you buy *double* the RAM you need to use, and run
> all memory operations in duplicate (on both DIMMs)? Ugh, that is one
> way to sell more RAM...

Double the processors *and* RAM and you have the method some mainframes 
use.  Once in a while, even triple.

Peace...  Sridhar