Re: Oracle Parallel Server vs RAC

"Sean M" <smckeown_at_earthlink.net> wrote in message news:3CC97439.32962515_at_earthlink.net...
>
>
> 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.
>

No. 8i introduced cache fusion for the transfer of read consistent buffers only. Therefore if you are seeking to select from a current block in another cache, that current block still gets transferred via the disk.

HJR
> > 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 - 16:57:02 CDT