От: Vincent van Leeuwen
Тема: Re: Tuning PostgreSQL
Дата: ,
Msg-id: 20030721162852.GN19009@md2.mediadesign.nl
(см: обсуждение, исходный текст)
Ответ на: Re: Tuning PostgreSQL  (Josh Berkus)
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 2003-07-21 09:06:10 -0700, Josh Berkus wrote:
> Alexander,
>
> > Hmmm. Seems to me that this setup would be better than one RAID5 with three
> > 36Gb disks, wouldn't you think so? With one RAID5 array, I would still have
> > the data and the WAL on one volume...
>
> Definitely.   As I've said, my experience with RAID5 is that with less than 5
> disks, it performs around 40% of a single scsi disk for large read-write
> operation on Postgres.
>
> If you have only 3 disks, I'd advocate one disk for WAL and one RAID 1 array
> for the database.
>

In this setup your database is still screwed if a single disk (the WAL disk)
stops working. You'll have to revert to your last backup if this happens. The
RAID-1 redundancy on your data disks buys you almost nothing: marginally
better performance and no real redundancy should a single disk fail.

I'd use RAID-5 if you absolutely cannot use more disks, but I would use
RAID-10 or two RAID-1 partitions if you can afford to use 4 disks.

Vincent van Leeuwen
Media Design - http://www.mediadesign.nl/


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