On Tue, 2006-01-31 at 21:53 -0800, Luke Lonergan wrote:
> Jeffrey,
> 
> On 1/31/06 8:09 PM, "Jeffrey W. Baker" <[EMAIL PROTECTED]> wrote:
> >> ... Prove it.
> > I think I've proved my point.  Software RAID1 read balancing provides
> > 0%, 300%, 100%, and 100% speedup on 1, 2, 4, and 8 threads,
> > respectively.  In the presence of random I/O, the results are even
> > better.
> > Anyone who thinks they have a single-threaded workload has not yet
> > encountered the autovacuum daemon.
> 
> Good data - interesting case.  I presume from your results that you had to
> make the I/Os non-overlapping (the "skip" option to dd) in order to get the
> concurrent access to work.  Why the particular choice of offset - 3.2GB in
> this case?

No particular reason.  8k x 100000 is what the last guy used upthread.
> 
> So - the bandwidth doubles in specific circumstances under concurrent
> workloads - not relevant to "Huge Data sets, simple queries", but possibly
> helpful for certain kinds of OLTP applications.

Ah, but someday Pg will be able to concurrently read from two
datastreams to complete a single query.  And that day will be glorious
and fine, and you'll want as much disk concurrency as you can get your
hands on.

-jwb


---------------------------(end of broadcast)---------------------------
TIP 4: Have you searched our list archives?

               http://archives.postgresql.org

Reply via email to