Re: Parallel Vacuum

From: Michael Stone
Subject: Re: Parallel Vacuum
Date: ,
Msg-id: 20070322171007.GH11402@mathom.us
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In response to: Re: Parallel Vacuum  (Dimitri)
Responses: Re: Parallel Vacuum  (Dimitri)
List: pgsql-performance

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Parallel Vacuum  (Dimitri, )
 Re: Parallel Vacuum  (Alvaro Herrera, )
  Re: Parallel Vacuum  (Dimitri, )
   Re: Parallel Vacuum  (Alvaro Herrera, )
    Re: Parallel Vacuum  (Dimitri, )
     Re: Parallel Vacuum  (Alvaro Herrera, )
     Re: Parallel Vacuum  (Michael Stone, )
      Re: Parallel Vacuum  (Dimitri, )
       Re: Parallel Vacuum  (Michael Stone, )
        Re: Parallel Vacuum  (Dimitri, )
         Re: Parallel Vacuum  (Michael Stone, )

On Thu, Mar 22, 2007 at 04:55:02PM +0100, Dimitri wrote:
>In my case I have several CPU on the server and quite powerful storage box
>which is not really busy with a single vacuum. So, my idea is quite simple -
>speed-up vacuum with parallel execution (just an algorithm):

Vacuum is I/O intensive, not CPU intensive. Running more of them will
probably make things slower rather than faster, unless each thing you're
vacuuming has its own (separate) disks. The fact that your CPU isn't
pegged while vacuuming suggests that your disk is already your
bottleneck--and doing multiple sequential scans on the same disk will
definitely be slower than doing one.

Mike Stone


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