Re: [SPAM?] Re: PG8 Tuning

From: Jeff Trout
Subject: Re: [SPAM?] Re: PG8 Tuning
Date: ,
Msg-id: B4099474-30C8-4549-A289-2EC4FD1FF4CB@torgo.978.org
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In response to: Re: [SPAM?] Re: PG8 Tuning  ("Jeffrey W. Baker")
List: pgsql-performance

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PG8 Tuning  ("Paul Johnson", )
 Re: PG8 Tuning  (Richard Huxton, )
 [SPAM?] Re: PG8 Tuning  (Steve Poe, )
  Re: [SPAM?] Re: PG8 Tuning  ("Jeffrey W. Baker", )
   Re: [SPAM?] Re: PG8 Tuning  (Jeff Trout, )
   Re: [SPAM?] Re: PG8 Tuning  (Josh Berkus, )
    Re: [SPAM?] Re: PG8 Tuning  (Alvaro Herrera <-ip.org>, )
     Re: [SPAM?] Re: PG8 Tuning  ("Joshua D. Drake", )
     Re: PG8 Tuning  (John A Meinel, )
      Re: PG8 Tuning  (Tom Lane, )
       Re: PG8 Tuning  (John A Meinel, )
        Re: PG8 Tuning  (Tom Lane, )
    Re: [SPAM?] Re: PG8 Tuning  (Michael Stone, )
     Re: PG8 Tuning  (Josh Berkus, )
  Re: [SPAM?] Re: PG8 Tuning  (Tom Arthurs, )
  Re: PG8 Tuning  (Mark Lewis, )
   Re: PG8 Tuning  (Michael Stone, )
 Re: PG8 Tuning  (Michael Stone, )
 Re: PG8 Tuning  ("Merlin Moncure", )

On Aug 11, 2005, at 12:58 PM, Jeffrey W. Baker wrote:

> Like Mr. Stone said earlier, this is pure dogma.  In my experience,
> xlogs on the same volume with data is much faster if both are on
> battery-backed write-back RAID controller memory.  Moving from this
> situation to xlogs on a single normal disk is going to be much
> slower in
> most cases.
>

This does also point one important point about performance.  Which is
a touch unfortunate (and expensive to test):  Your milage may vary on
any of these improvements.   Some people have 0 problems and
incredible performance with say, 1000 shared_bufs and the WAL on the
same disk..  Others need 10k shared bufs and wal split over a 900
spindle raid with data spread across 18 SAN's...
Unfortunately there is no one true way :(

The best bet (which is great if you can): Try out various settings..
if you still run into problems look into some more hardware.. see if
you can borrow any or fabricate a "poor man"'s equivalent for testing.

--
Jeff Trout <>
http://www.jefftrout.com/
http://www.stuarthamm.net/




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From: Jeff Trout
Date:
Subject: Re: [SPAM?] Re: PG8 Tuning
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Subject: Re: Mostly read performance (2 replies)