Re: PostgreSQL as a local in-memory cache

On 6/15/10 10:37 AM, Chris Browne wrote:
> swampler@noao.edu (Steve Wampler) writes:
>> Or does losing WAL files mandate a new initdb?
>
> Losing WAL would mandate initdb, so I'd think this all fits into the
> set of stuff worth putting onto ramfs/tmpfs.  Certainly it'll all be
> significant to the performance focus.

I'd like to see some figures about WAL on RAMfs vs. simply turning off
fsync and full_page_writes.  Per Gavin's tests, PostgreSQL is already
close to TokyoCabinet/MongoDB performance just with those turned off; I
wonder if actually having the WAL on a memory partition would make any
real difference in throughput.

I've seen a lot of call for this recently, especially since PostgreSQL
seems to be increasingly in use as a reporting server for Hadoop.  Might
be worth experimenting with just making wal writing a no-op.  We'd also
want to disable checkpointing, of course.

--
                                  -- Josh Berkus
                                     PostgreSQL Experts Inc.
                                     http://www.pgexperts.com