Re: How to improve db performance with $7K?

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От Tom Lane
Тема Re: How to improve db performance with $7K?
Дата
Msg-id 446.1113489854@sss.pgh.pa.us
обсуждение исходный текст
Ответ на Re: How to improve db performance with $7K?  (Kevin Brown)
Ответы Re: How to improve db performance with $7K?  (Kevin Brown)
Re: How to improve db performance with $7K?  (Matthew Nuzum)
Список pgsql-performance
Дерево обсуждения
How to improve db performance with $7K?  (Steve Poe, )
 Re: How to improve db performance with $7K?  (Tom Lane, )
  Re: How to improve db performance with $7K?  (Steve Poe, )
 Re: How to improve db performance with $7K?  (Will LaShell, )
 Re: How to improve db performance with $7K?  ("Joshua D. Drake", )
  Re: How to improve db performance with $7K?  (Steve Poe, )
   Re: How to improve db performance with $7K?  (Bjoern Metzdorf, )
    Re: How to improve db performance with $7K?  (Josh Berkus, )
     Re: How to improve db performance with $7K?  (Steve Poe, )
      Re: How to improve db performance with $7K?  (Cott Lang, )
       Re: How to improve db performance with $7K?  (Steve Poe, )
        Re: How to improve db performance with $7K?  (Cott Lang, )
         Follow-Up: How to improve db performance with $7K?  (Steve Poe, )
          Re: Follow-Up: How to improve db performance with $7K?  (Thomas F.O'Connell, )
           Re: Follow-Up: How to improve db performance with $7K?  (Kevin Brown, )
            Re: Follow-Up: How to improve db performance with $7K?  ("Steinar H. Gunderson", )
            Re: Follow-Up: How to improve db performance with $7K?  (Thomas F.O'Connell, )
          Re: Follow-Up: How to improve db performance with $7K?  (Vivek Khera, )
           Re: Follow-Up: How to improve db performance with $7K?  (Will LaShell, )
     Re: How to improve db performance with $7K?  (Steve Poe, )
    Re: Follow-Up: How to improve db performance with $7K?  (PFC, )
     Re: Follow-Up: How to improve db performance with $7K?  ("Steinar H. Gunderson", )
   Re: How to improve db performance with $7K?  (PFC, )
    Re: How to improve db performance with $7K?  (Dave Cramer, )
     Re: How to improve db performance with $7K?  (Greg Stark, )
     Re: How to improve db performance with $7K?  (Alex Turner, )
      Re: How to improve db performance with $7K?  (Steve Poe, )
       Re: How to improve db performance with $7K?  (Alex Turner, )
        Re: How to improve db performance with $7K?  (Vivek Khera, )
         Re: How to improve db performance with $7K?  (Alex Turner, )
        Re: How to improve db performance with $7K?  (William Yu, )
         Re: How to improve db performance with $7K?  (Alex Turner, )
          Re: How to improve db performance with $7K?  (William Yu, )
           Re: How to improve db performance with $7K?  (Alex Turner, )
            Re: How to improve db performance with $7K?  ("Jim C. Nasby", )
             Re: How to improve db performance with $7K?  (Alex Turner, )
              Re: How to improve db performance with $7K?  (Alex Turner, )
               Re: How to improve db performance with $7K?  (Alex Turner, )
              Re: How to improve db performance with $7K?  (Greg Stark, )
               Re: How to improve db performance with $7K?  (Alex Turner, )
               Re: How to improve db performance with $7K?  (Tom Lane, )
                Re: How to improve db performance with $7K?  (Kevin Brown, )
                 Re: How to improve db performance with $7K?  (Greg Stark, )
                  Re: How to improve db performance with $7K?  (Kevin Brown, )
                   Re: How to improve db performance with $7K?  (Tom Lane, )
                    Re: How to improve db performance with $7K?  (Kevin Brown, )
                     Re: How to improve db performance with $7K?  (Alex Turner, )
                      Re: How to improve db performance with $7K?  (PFC, )
                     Re: How to improve db performance with $7K?  (Tom Lane, )
                      Re: How to improve db performance with $7K?  (Kevin Brown, )
                       Re: How to improve db performance with $7K?  (Tom Lane, )
                        Re: How to improve db performance with $7K?  (Kevin Brown, )
                      Re: How to improve db performance with $7K?  (Greg Stark, )
                     Re: How to improve db performance with $7K?  (Vivek Khera, )
                      Re: How to improve db performance with $7K?  ("Joshua D. Drake", )
                       Re: How to improve db performance with $7K?  (Vivek Khera, )
                      Re: How to improve db performance with $7K?  (Kevin Brown, )
                    Re: How to improve db performance with $7K?  (Matthew Nuzum, )
                     Re: How to improve db performance with $7K?  ("Jim C. Nasby", )
                   Re: How to improve db performance with $7K?  (Rosser Schwarz, )
                    Re: How to improve db performance with $7K?  (Kevin Brown, )
                   Re: How to improve db performance with $7K?  (Greg Stark, )
                   Re: How to improve db performance with $7K?  (Bruce Momjian, )
                    Re: How to improve db performance with $7K?  (Alex Turner, )
                     Re: How to improve db performance with $7K?  (Alvaro Herrera, )
                     Re: How to improve db performance with $7K?  (Bruce Momjian, )
              Re: How to improve db performance with $7K?  ("Douglas J. Trainor", )
               Re: How to improve db performance with $7K?  (, )
                Re: How to improve db performance with $7K?  (Alex Turner, )
                 Re: How to improve db performance with $7K?  (, )
            Re: How to improve db performance with $7K?  ("Douglas J. Trainor", )
            Re: How to improve db performance with $7K?  (PFC, )
             Re: How to improve db performance with $7K?  (Alan Stange, )
    Re: How to improve db performance with $7K?  (Dave Cramer, )
 Re: How to improve db performance with $7K?  ("Alexander Kirpa", )
 Re: How to improve db performance with $7K?  ("Mohan, Ross", )
 Re: How to improve db performance with $7K?  ("Matthew Nuzum", )
  Re: How to improve db performance with $7K?  (Greg Stark, )
   Re: How to improve db performance with $7K?  (PFC, )
  Re: How to improve db performance with $7K?  (Tom Lane, )
 Re: How to improve db performance with $7K?  ("Dave Held", )
 Re: How to improve db performance with $7K?  ("Mohan, Ross", )
  Re: How to improve db performance with $7K?  (Steve Poe, )
   Re: How to improve db performance with $7K?  ("Joshua D. Drake", )
   Re: How to improve db performance with $7K?  (William Yu, )
    Re: How to improve db performance with $7K?  (Greg Stark, )
     Re: How to improve db performance with $7K?  (Alex Turner, )
      Re: How to improve db performance with $7K?  (Greg Stark, )
       Re: How to improve db performance with $7K?  (Alex Turner, )
        Re: How to improve db performance with $7K?  (Jacques Caron, )
         Re: How to improve db performance with $7K?  (Alex Turner, )
          Re: How to improve db performance with $7K?  (Alex Turner, )
           Re: How to improve db performance with $7K?  (Jacques Caron, )
            Re: How to improve db performance with $7K?  (Alex Turner, )
          Re: How to improve db performance with $7K?  (Jacques Caron, )
         Re: How to improve db performance with $7K?  (Greg Stark, )
        Re: How to improve db performance with $7K?  (Alan Stange, )
        Re: How to improve db performance with $7K?  (John A Meinel, )
         Re: How to improve db performance with $7K?  (Alex Turner, )
          Re: How to improve db performance with $7K?  ("Joshua D. Drake", )
           Re: How to improve db performance with $7K?  (Alex Turner, )
        Re: How to improve db performance with $7K?  (Steve Poe, )
         Re: How to improve db performance with $7K?  (Alex Turner, )
     Re: How to improve db performance with $7K?  (Jacques Caron, )
      Re: How to improve db performance with $7K?  ("Jim C. Nasby", )
     Re: How to improve db performance with $7K?  (William Yu, )
 Re: How to improve db performance with $7K?  ("Dave Held", )
 Re: How to improve db performance with $7K?  ("Mohan, Ross", )
 Re: How to improve db performance with $7K?  ("Dave Held", )
  Re: How to improve db performance with $7K?  ("Jim C. Nasby", )
 Re: How to improve db performance with $7K?  ("Mohan, Ross", )
  Re: How to improve db performance with $7K?  ("Jim C. Nasby", )
   Re: How to improve db performance with $7K?  (Alex Turner, )
 Re: How to improve db performance with $7K?  ("Dave Held", )
  Re: How to improve db performance with $7K?  (Alex Turner, )
   Re: How to improve db performance with $7K?  (William Yu, )
 Re: How to improve db performance with $7K?  ("Mohan, Ross", )
  Re: How to improve db performance with $7K?  (Bruce Momjian, )
   Re: How to improve db performance with $7K?  (, )
    Re: How to improve db performance with $7K?  ("Jim C. Nasby", )
     What to do with 6 disks?  (Jeff Frost, )
      Re: What to do with 6 disks?  ("Jim C. Nasby", )
      Re: What to do with 6 disks?  (Josh Berkus, )
       Re: Opteron vs Xeon (Was: What to do with 6 disks?)  (Jeff Frost, )
        Re: Opteron vs Xeon (Was: What to do with 6 disks?)  ("J. Andrew Rogers", )
         Re: Opteron vs Xeon (Was: What to do with 6 disks?)  (Jeff Frost, )
          Re: Opteron vs Xeon (Was: What to do with 6 disks?)  (William Yu, )
        Re: Opteron vs Xeon (Was: What to do with 6 disks?)  (Vivek Khera, )
       Re: What to do with 6 disks?  (Vivek Khera, )
      Re: What to do with 6 disks?  (William Yu, )
 Re: How to improve db performance with $7K?  ("Mohan, Ross", )
  Re: How to improve db performance with $7K?  (Bruce Momjian, )
  Re: How to improve db performance with $7K?  (Dawid Kuroczko, )
 Re: How to improve db performance with $7K?  ("Mohan, Ross", )
 Re: How to improve db performance with $7K?  ("Mohan, Ross", )
 Re: How to improve db performance with $7K?  ("Mohan, Ross", )
 Re: How to improve db performance with $7K?  ("Dave Held", )
 Re: How to improve db performance with $7K?  ("Mohan, Ross", )
Kevin Brown <> writes:
> I really don't see how this is any different between a system that has
> tagged queueing to the disks and one that doesn't.  The only
> difference is where the queueing happens.  In the case of SCSI, the
> queueing happens on the disks (or at least on the controller).  In the
> case of SATA, the queueing happens in the kernel.

That's basically what it comes down to: SCSI lets the disk drive itself
do the low-level I/O scheduling whereas the ATA spec prevents the drive
from doing so (unless it cheats, ie, caches writes).  Also, in SCSI it's
possible for the drive to rearrange reads as well as writes --- which
AFAICS is just not possible in ATA.  (Maybe in the newest spec...)

The reason this is so much more of a win than it was when ATA was
designed is that in modern drives the kernel has very little clue about
the physical geometry of the disk.  Variable-size tracks, bad-block
sparing, and stuff like that make for a very hard-to-predict mapping
from linear sector addresses to actual disk locations.  Combine that
with the fact that the drive controller can be much smarter than it was
twenty years ago, and you can see that the case for doing I/O scheduling
in the kernel and not in the drive is pretty weak.

            regards, tom lane

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