Re: Oracle Parallel Server vs RAC

Chuck wrote:
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Tell them with OPS they will need to redesign their applications or
> they risk VERY poor performance.

That depends on how they're using OPS. If they're using it to scale up, then I agree. If they're only using it for redundancy/failover (i.e. OPFS), then there's no need to partition anything since users are only connecting to one node at a time.

> With OPS your app needs to be
> partitioned so that there is little or no pinging (requests for the
> same blocks on more than one node). This is because blocks are passed
> between nodes via physical disk i/o. Each time one node requests a
> block that is already in another nodes cache, there are at least two
> physical I/Oss needed to get it there.

Depends on the kind of block request. If the request is to merely select the block, and IIRC, 8i OPS can send that block across the interlink without a ping to disk.

> RAC however pings blocks over
> the high speed interconnect virtually eliminating any performance
> bottleneck.

Well, that's the marketing at least. ;) RAC is definitely a major improvement. But it still isn't free.  

> Unless your application can be partitioned, scalability is nill with
> OPS. With RAC scalability is close to linear and existing
> applications port well just as they are.

There's still overhead with RAC. And there's still managability requirements. RAC's locking mechanisms are very different, so you may still want to do some structural work at the db level, like using bitmapped segments instead of free lists/groups, etc. However, unless you have some overarching reason to use OPS, then skip it. You'll be much happier w/RAC.

Regards,
Sean Received on Fri Apr 26 2002 - 10:37:25 CDT