Re: Occasional giant spikes in CPU load

От: Bruce Momjian
Тема: Re: Occasional giant spikes in CPU load
Дата: ,
Msg-id: 201004142158.o3ELwXL09621@momjian.us
(см: обсуждение, исходный текст)
Ответ на: Re: Occasional giant spikes in CPU load  (Craig James)
Список: pgsql-performance

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indexes in partitioned tables - again  (Samuel Gendler, )
 Re: indexes in partitioned tables - again  (Robert Haas, )
  Occasional giant spikes in CPU load  (Craig James, )
   Re: Occasional giant spikes in CPU load  ("Joshua D. Drake", )
    Re: Occasional giant spikes in CPU load  (Craig James, )
     Re: Occasional giant spikes in CPU load  ("Joshua D. Drake", )
      Re: Occasional giant spikes in CPU load  (Craig James, )
       Re: Occasional giant spikes in CPU load  (David Rees, )
       Re: Occasional giant spikes in CPU load  (Tom Lane, )
       Re: Occasional giant spikes in CPU load  (Alan Hodgson, )
     Re: Occasional giant spikes in CPU load  ("Joshua D. Drake", )
   Re: Occasional giant spikes in CPU load  (Greg Smith, )
   Re: Occasional giant spikes in CPU load  (Tom Lane, )
    Re: Occasional giant spikes in CPU load  (Craig James, )
     Re: Occasional giant spikes in CPU load  (Steve Crawford, )
   Re: Occasional giant spikes in CPU load  (David Rees, )
    Re: Occasional giant spikes in CPU load  (Robert Haas, )
     Re: Occasional giant spikes in CPU load  (Craig James, )
      Re: Occasional giant spikes in CPU load  (David Rees, )
       Re: Occasional giant spikes in CPU load  (Robert Haas, )
        Re: Occasional giant spikes in CPU load  (Craig James, )
         Re: Occasional giant spikes in CPU load  ("Joshua D. Drake", )
         Re: Occasional giant spikes in CPU load  (Greg Smith, )
         Re: Occasional giant spikes in CPU load  (Tom Lane, )
          Re: Occasional giant spikes in CPU load  (Craig James, )
           Re: Occasional giant spikes in CPU load  (Tom Lane, )
            Re: Occasional giant spikes in CPU load  (Craig James, )
             Re: Occasional giant spikes in CPU load  ("Kevin Grittner", )
              Re: Occasional giant spikes in CPU load  (Craig James, )
             Re: Occasional giant spikes in CPU load  (Greg Smith, )
             Re: Occasional giant spikes in CPU load  (Tom Lane, )
              pgbench results on a new server  (Craig James, )
               Re: pgbench results on a new server  (Scott Marlowe, )
               Re: pgbench results on a new server  (Greg Smith, )
                Re: pgbench results on a new server  (Craig James, )
                 Re: pgbench results on a new server  (Merlin Moncure, )
                  Two fast searches turn slow when used with OR clause  (Craig James, )
                   Re: Two fast searches turn slow when used with OR clause  (Robert Haas, )
                 Re: pgbench results on a new server  (Greg Smith, )
           Re: Occasional giant spikes in CPU load  (Rajesh Kumar Mallah, )
         Re: Occasional giant spikes in CPU load  ("Joshua D. Drake", )
      Re: Occasional giant spikes in CPU load  (Bruce Momjian, )
    Re: Occasional giant spikes in CPU load  (Greg Smith, )
   Re: Occasional giant spikes in CPU load  ("Joshua D. Drake", )

Craig James wrote:
> On 4/7/10 5:47 PM, Robert Haas wrote:
> > On Wed, Apr 7, 2010 at 6:56 PM, David Rees<>  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  <>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com


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