Re: question about readonly instances

On 19 May 2011 09:05, John R Pierce <pierce(at)hogranch(dot)com> wrote:

> On 05/18/11 11:39 PM, Szymon Guz wrote:
>
>>
>> thanks for the answer. It is not a problem to have 3 oracle instances, in
>> fact there will be hundreds of them probably, but could also be hundreds of
>> Postgres instances :)
>>
>
> do you have any idea how EXPENSIVE 100s of Oracle RAC nodes are annually?
>
> to share block storage between cluster nodes requires a cluster-aware file
> system, as conventional file systems do not expect the disk files to change
> behind their back. these cluster-aware file systems have a bunch of
> overhead in maintaining cache coherency between nodes, and such.
>
> as far as I know, postgres can not be run on a read only file system,
> further its shared_buffer caches couldn't possibly be aware of other nodes
> modifying blocks that happen to be cached.
>
>
>
Well,
I have no idea how expensive it is, but fortunately that's not my problem :)
I was only asked about the possibility of running Postgres that way.
And by the way: how expensive is that?

regards
Szymon