Re: Huge Data sets, simple queries

От: Kevin
Тема: Re: Huge Data sets, simple queries
Дата: ,
Msg-id: 43DF9D93.3030602@drule.org
(см: обсуждение, исходный текст)
Ответ на: Re: Huge Data sets, simple queries  ("Luke Lonergan")
Список: pgsql-performance

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Huge Data sets, simple queries  ("Mike Biamonte", )
 Re: Huge Data sets, simple queries  ("Jeffrey W. Baker", )
 Re: Huge Data sets, simple queries  (Tom Lane, )
  Re: Huge Data sets, simple queries  ("Jeffrey W. Baker", )
   Re: Huge Data sets, simple queries  (Tom Lane, )
    Re: Huge Data sets, simple queries  (Tom Lane, )
 Re: Huge Data sets, simple queries  ("Luke Lonergan", )
  Re: Huge Data sets, simple queries  (hubert depesz lubaczewski, )
   Re: Huge Data sets, simple queries  (Michael Stone, )
  Re: Huge Data sets, simple queries  ("Jim C. Nasby", )
   Re: Huge Data sets, simple queries  ("Luke Lonergan", )
    Re: Huge Data sets, simple queries  (Kevin, )
    Re: Huge Data sets, simple queries  ("Jim C. Nasby", )
     Re: Huge Data sets, simple queries  ("Luke Lonergan", )
      Re: Huge Data sets, simple queries  ("Jim C. Nasby", )
       Re: Huge Data sets, simple queries  ("Luke Lonergan", )
        Re: Huge Data sets, simple queries  ("Jim C. Nasby", )
    Re: Huge Data sets, simple queries  ("Jeffrey W. Baker", )
     Re: Huge Data sets, simple queries  ("Luke Lonergan", )
      Re: Huge Data sets, simple queries  (PFC, )
       Re: Huge Data sets, simple queries  ("Luke Lonergan", )
      Re: Huge Data sets, simple queries  ("Steinar H. Gunderson", )
       Re: Huge Data sets, simple queries  ("Luke Lonergan", )
      Re: Huge Data sets, simple queries  ("Jeffrey W. Baker", )
       Re: Huge Data sets, simple queries  ("Luke Lonergan", )
        Re: Huge Data sets, simple queries  ("Jeffrey W. Baker", )
         Re: Huge Data sets, simple queries  (PFC, )
          Re: Huge Data sets, simple queries  ("Luke Lonergan", )
           Re: Huge Data sets, simple queries  ("Steinar H. Gunderson", )
           Re: Huge Data sets, simple queries  (Mike Rylander, )
         Re: Huge Data sets, simple queries  ("Luke Lonergan", )
       Re: Huge Data sets, simple queries  (Michael Stone, )
     Re: Huge Data sets, simple queries  (Alan Stange, )
 Re: Huge Data sets, simple queries  ("Luke Lonergan", )
  Re: Huge Data sets, simple queries  ("Jeffrey W. Baker", )
  Re: Huge Data sets, simple queries  (Charles Sprickman, )
   Re: Huge Data sets, simple queries  ("Luke Lonergan", )
  Re: Huge Data sets, simple queries  (hubert depesz lubaczewski, )
   Re: Huge Data sets, simple queries  ("Luke Lonergan", )
 Re: Huge Data sets, simple queries  (Michael Adler, )
 Re: Huge Data sets, simple queries  ("Craig A. James", )

Luke Lonergan wrote:
> Jim,
>
> On 1/30/06 12:25 PM, "Jim C. Nasby" <> wrote:
>
>
>> Why divide by 2? A good raid controller should be able to send read
>> requests to both drives out of the mirrored set to fully utilize the
>> bandwidth. Of course, that probably won't come into play unless the OS
>> decides that it's going to read-ahead fairly large chunks of the table
>> at a time...
>>
>
> I've not seen one that does, nor would it work in the general case IMO.  In
> RAID1 writes are duplicated and reads come from one of the copies.  You
> could alternate read service requests to minimize rotational latency, but
> you can't improve bandwidth.
>
> - Luke
>
>
For Solaris's software raid, the default settings for raid-1 sets is:
round-robin read, parallel write.   I assumed this mean't it would give
similar read performance to raid-0, but I've never benchmarked it.

-Kevin


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