Re: Upgrade to big SUN box or RAC for data warehouse?

On 23 Jul 2003 11:28:05 -0700, JEDIDIAH <jedithezealot_at_yahoo.com> wrote:

> Quarkman <quarkman_at_myrealbox.com> wrote in message
> news:<oprsqa790tr9lm4d_at_haydn>...
>> On Tue, 22 Jul 2003 15:01:10 -0400, Ryan <rgaffuri_at_cox.net> wrote:
>>
>> > why would implementing RAC increase I/O? is that because of the 2
>> phase
>> > commit? So you have to write to multiple datafiles?
>>
>> No.
>>
>> It may increase I/O for a number of reasons. A buffer in Instance A may
>> have to be flushed for no other reason than Instance B has a past image
>> of that buffer, and *it* needs to over-write its contents. The problem
>> of forced disk writes (one instance making another instance do some I/O
>> it wouldn't necessarily want to do on its own) has not been abolished in
>> RAC (but it's better than it was in OPS).
>>
>> Secondly, the interconnect is not of infinite bandwidth, therefore
>> reserving it for the transport of buffers which really, really need to
>> be shipped to other instances in the shortest possible time may be quite
>> important. Therefore, you use GC_FILES_TO_LOCKS to switch off cache
>> fusion
>
> Can you elaborate on this please for those of us that have only
> experienced RAC as spectators? Can you provide some meaningful
> examples?
>
> [deletia]
>

Elaborate on what bit? The interconnect being a bottleneck? Or using GC_FILES_TO_LOCKS to switch off cache fusion? Or forced disk writes?

I'm not sure what would qualify as a meaningful example, either!

~QM Received on Wed Jul 23 2003 - 15:36:02 CDT