Quoth Ron Mayer <rm_pg@cheapcomplexdevices.com>:
> Merlin Moncure wrote:
>> ...You need to build a bigger, faster box with lots of storage...
>> Clustering ... B: will cost you more, not less
>
>
> Is this still true when you get to 5-way or 17-way systems?
>
> My (somewhat outdated) impression is that up to about 4-way systems
> they're price competitive; but beyond that, I thought multiple cheap
> servers scales much more afordably than large servers. Certainly
> at the point of a 129-CPU system I bet you're better off with a
> network of cheap servers.
Not necessarily.
If you have 129 boxes that you're trying to keep synced, it is likely
that the cost of syncing them will be greater than the other write
load.
If the problem being addressed is that a 4-way box won't handle the
transaction load, it is unlikely that building a cluster of _smaller_
machines will help terribly much.
The reason to "cluster" in the context of a transactional system is
that you need improved _reliability_.
Since communications between servers is _thousands_ of times slower
than communicating with local memory, you have to be willing to live
with an ENORMOUS degradation of performance when hosts are
synchronized.
And if "real estate" has a cost, where you have to pay for rack space,
having _fewer_ machines is preferable to having more.
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