От: Ron Johnson
Тема: Re: Tuning PostgreSQL
Дата: ,
Msg-id: 1059502102.7505.176.camel@haggis
(см: обсуждение, исходный текст)
Ответ на: Re: Tuning PostgreSQL  ("scott.marlowe")
Ответы: Re: Tuning PostgreSQL  ("scott.marlowe")
Список: pgsql-performance

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Tuning PostgreSQL  ("Alexander Priem", )
 Re: Tuning PostgreSQL  ("Shridhar Daithankar", )
 Re: Tuning PostgreSQL  ("Shridhar Daithankar", )
  Re: Tuning PostgreSQL  ("Alexander Priem", )
  Re: Tuning PostgreSQL  (Ang Chin Han, )
   Re: Tuning PostgreSQL  ("Shridhar Daithankar", )
    Re: Tuning PostgreSQL  (Ang Chin Han, )
     Re: Tuning PostgreSQL  ("Shridhar Daithankar", )
  Re: Tuning PostgreSQL  ("Alexander Priem", )
   Re: Tuning PostgreSQL  ("Shridhar Daithankar", )
    Re: Tuning PostgreSQL  ("Alexander Priem", )
  Re: Tuning PostgreSQL  (Ron Johnson, )
  Re: Tuning PostgreSQL  ("Alexander Priem", )
   Re: Tuning PostgreSQL  (Ron Johnson, )
   Re: Tuning PostgreSQL  (Andrew McMillan, )
    Re: Tuning PostgreSQL  ("Arjen van der Meijden", )
     Re: Tuning PostgreSQL  (Tom Lane, )
     Re: Tuning PostgreSQL  ("Balazs Wellisch", )
      Re: Tuning PostgreSQL  (Josh Berkus, )
 Re: Tuning PostgreSQL  ("Roman Fail", )
  Re: Tuning PostgreSQL  ("Alexander Priem", )
   Re: Tuning PostgreSQL  (Josh Berkus, )
    Re: Tuning PostgreSQL  (Vincent van Leeuwen, )
  Re: Tuning PostgreSQL  ("Alexander Priem", )
   Re: Tuning PostgreSQL  (Vincent van Leeuwen, )
    Re: Tuning PostgreSQL  (Bruno Wolff III, )
  Re: Tuning PostgreSQL  ("Alexander Priem", )
   Re: Tuning PostgreSQL  (Andrew Sullivan, )
   Re: Tuning PostgreSQL  ("Jim C. Nasby", )
    Re: Tuning PostgreSQL  ("scott.marlowe", )
     Re: Tuning PostgreSQL  (Greg Stark, )
      Re: Tuning PostgreSQL  (Ron Johnson, )
     Re: Tuning PostgreSQL  (Vivek Khera, )
      Re: Tuning PostgreSQL  (Ron Johnson, )
       Re: Tuning PostgreSQL  ("scott.marlowe", )
        Re: Tuning PostgreSQL  (Ron Johnson, )
         Re: Tuning PostgreSQL  ("scott.marlowe", )
          Re: Tuning PostgreSQL  (Ron Johnson, )
           Re: Tuning PostgreSQL  ("scott.marlowe", )
            Re: Tuning PostgreSQL  (Ron Johnson, )
             Re: Tuning PostgreSQL, pt 2  (Ron Johnson, )
          Re: Tuning PostgreSQL  (Vivek Khera, )
      Re: Tuning PostgreSQL  (Will LaShell, )
  Re: Tuning PostgreSQL  ("Alexander Priem", )
   Re: Tuning PostgreSQL  (Ron Johnson, )
  Re: Tuning PostgreSQL  (Vivek Khera, )
 'View'-performance  ("Alexander Priem", )
  Re: 'View'-performance  (Tom Lane, )

On Tue, 2003-07-29 at 11:18, scott.marlowe wrote:
> On 29 Jul 2003, Ron Johnson wrote:
>
> > On Tue, 2003-07-29 at 10:14, Vivek Khera wrote:
> > > >>>>> "GS" == Greg Stark <> writes:
> > >
> > > GS> "scott.marlowe" <> writes:
> > >
> > > GS> But you have to actually test your setup in practice to see if it
> > > GS> hurts. A big data warehousing system will be faster under RAID5
> > > GS> than under RAID1+0 because of the extra disks in the
> > > GS> stripeset. The more disks in the stripeset the more bandwidth you
> > > GS> get.
> > >
> > > Anyone have ideas on 14 spindles?  I just ordered a disk subsystem
> > > with 14 high speed (U320 15kRPM) SCSI disks to hook up with a dell
> > > PERC3/DC controller (only 128MB cache, though).
> >
> > 14 drives on one SCSI card, eh?  I'd be worried about saturating
> > the bus.
>
> I'm pretty sure those PERCs are based on the megaraid cards, which can
> handle 3 or 4 channels each...

Each with 14 devices?  If so, isn't that a concentrated point of
failure, even if the channels are 1/2 full?

> > Maybe it's an old rule of thumb, but I would fill a SCSI chain
> > more than half full.
>
> It's an old rule of thumb, but it still applies, it just takes more drives
> to saturate the channel.  Figure ~ 30 to 50 MBytes a second per drive, on
> a U320 port it would take 10 drives to saturate it, and considering random
> accesses will be much slower than the max ~30 megs a second off the
> platter rate, it might take more than the max 14 drives to saturate U320.

Ok.  You'd still saturate the 133MB/s PCI bus at 133/30 = 4.4 drives.

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