Re: Occasional giant spikes in CPU load

Craig James wrote:
> On 4/7/10 5:47 PM, Robert Haas wrote:
> > On Wed, Apr 7, 2010 at 6:56 PM, David Rees<drees76@gmail.com>  wrote:
> >>> max_fsm_pages = 16000000
> >>> max_fsm_relations = 625000
> >>> synchronous_commit = off
> >>
> >> You are playing with fire here.  You should never turn this off unless
> >> you do not care if your data becomes irrecoverably corrupted.
> >
> > That is not correct.  Turning off synchronous_commit is sensible if
> > you don't mind losing the last few transactions on a crash.  What will
> > corrupt your database is if you turn off fsync.
>
> A bit off the original topic, but ...
>
> I set it this way because I was advised that with a battery-backed
> RAID controller, this was a safe setting.  Is that not the case?

To get good performance, you can either get a battery-backed RAID
controller or risk losing a few transaction with synchronous_commit =
off.  If you already have a battery-backed RAID controller, there is
little benefit to turning synchronous_commit off, and some major
downsides (possible data loss).

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com