On 19 May 2011 09:05, John R Pierce <pie...@hogranch.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
