Re: Dual Xeon + HW RAID question

From: Bruce Momjian
Subject: Re: Dual Xeon + HW RAID question
Date: ,
Msg-id: 200307211907.h6LJ7YV03382@candle.pha.pa.us
(view: Whole thread, Raw)
In response to: Re: Dual Xeon + HW RAID question  (SZUCS Gábor)
List: pgsql-performance

Tree view

Dual Xeon + HW RAID question  ("alexandre arruda paes :: aldeia digital", )
 Re: Dual Xeon + HW RAID question  (Rod Taylor, )
 Re: Dual Xeon + HW RAID question  ("Nikolaus Dilger", )
  [OT] Such incredible h/w (was Re: Dual Xeon + HW RAID question)  (Ron Johnson, )
  Re: Dual Xeon + HW RAID question  (Andrew Sullivan, )
  Re: Dual Xeon + HW RAID question  (SZUCS Gábor, )
   Re: Dual Xeon + HW RAID question  ("alexandre paes :: aldeia digital", )
   Re: Dual Xeon + HW RAID question  (Bruce Momjian, )
    Re: Dual Xeon + HW RAID question  ("Mindaugas Riauba", )
     Re: Dual Xeon + HW RAID question  (Bruce Momjian, )
      Re: Dual Xeon + HW RAID question  (SZUCS Gábor, )
       Re: Dual Xeon + HW RAID question  (Jord Tanner, )
        Re: Dual Xeon + HW RAID question  (Bruce Momjian, )
         Re: Dual Xeon + HW RAID question  (Jord Tanner, )
          Re: Dual Xeon + HW RAID question  (Bruce Momjian, )
           Re: Dual Xeon + HW RAID question  (Jord Tanner, )
       Re: Dual Xeon + HW RAID question  (Bruce Momjian, )

SZUCS G�bor wrote:
> Alexandre,
>
> I missed your orig. post, but AFAIK multiprocessing kernels will handle HT
> CPUs as 2 CPUs each. Thus, our dual Xeon 2.4 is recognized as 4 Xeon 2.4
> CPUs.
>
> This way, I don't think HT would improve any single query (afaik no postgres
> process uses more than one cpu), but overall multi-query performance has to
> improve.

When you use hyperthreading, each virtual cpu runs at 70% of a full CPU,
so hyperthreading could be slower than non-hyperthreading.  On a fully
loaded dual cpu system, you are looking at 2.8 cpu's (0.70 * 4), while
if it isn't loaded, you are looking at slowing down if you are only
using 1 or 2 cpu's.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
                 |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073


pgsql-performance by date:

From: Christopher Browne
Date:
Subject: Re: PGAvd
From: "Alexander Priem"
Date:
Subject: Re: Tuning PostgreSQL