От: Mark Kirkwood
Тема: Re: Raid 10 chunksize
Дата: ,
Msg-id: 49C9A314.6050302@paradise.net.nz
(см: обсуждение, исходный текст)
Ответ на: Re: Raid 10 chunksize  (Scott Marlowe)
Ответы: Re: Raid 10 chunksize  (Jerry Champlin)
Re: Raid 10 chunksize  (Mark Kirkwood)
Список: pgsql-performance

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Raid 10 chunksize  (Mark Kirkwood, )
 Re: Raid 10 chunksize  (Scott Carey, )
  Re: Raid 10 chunksize  (David Rees, )
   Re: Raid 10 chunksize  (Greg Smith, )
 Re: Raid 10 chunksize  (Scott Marlowe, )
  Re: Raid 10 chunksize  (Mark Kirkwood, )
   Re: Raid 10 chunksize  (Jerry Champlin, )
   Re: Raid 10 chunksize  (Mark Kirkwood, )
    Re: Raid 10 chunksize  (Scott Carey, )
     Re: Raid 10 chunksize  (Mark Kirkwood, )
      Re: Raid 10 chunksize  (Mark Kirkwood, )
 Re: Raid 10 chunksize  (Greg Smith, )
  Re: Raid 10 chunksize  (Scott Carey, )
   Re: Raid 10 chunksize  (Merlin Moncure, )
    Re: Raid 10 chunksize  (Scott Carey, )
     Re: Raid 10 chunksize  (Merlin Moncure, )
     Re: Raid 10 chunksize  (Scott Carey, )
  Re: Raid 10 chunksize  (Mark Kirkwood, )
   Re: Raid 10 chunksize  (Greg Smith, )
    Re: Raid 10 chunksize  (Mark Kirkwood, )
 Re: Raid 10 chunksize  (Stef Telford, )
  Re: Raid 10 chunksize  (Mark Kirkwood, )
   Re: Raid 10 chunksize  (Scott Carey, )
    Re: Raid 10 chunksize  (Scott Carey, )
     Re: Raid 10 chunksize  (Mark Kirkwood, )
      Re: Raid 10 chunksize  (Stef Telford, )
       Re: Raid 10 chunksize  (Greg Smith, )
        Re: Raid 10 chunksize  (Stef Telford, )
         Re: Raid 10 chunksize  (Scott Marlowe, )
          Re: Raid 10 chunksize  (Stef Telford, )
           Re: Raid 10 chunksize  (Scott Marlowe, )
            Re: Raid 10 chunksize  (Greg Smith, )
             Re: Raid 10 chunksize  (Matthew Wakeling, )
              Re: Raid 10 chunksize  (Scott Marlowe, )
            Re: Raid 10 chunksize  (Scott Carey, )
             Re: Raid 10 chunksize  (, )
             Re: Raid 10 chunksize  (Scott Marlowe, )
           Re: Raid 10 chunksize  (Matthew Wakeling, )
            Re: Raid 10 chunksize  (Scott Marlowe, )
            Re: Raid 10 chunksize  (Stef Telford, )
            Re: Raid 10 chunksize  (Scott Carey, )
          Re: Raid 10 chunksize  (Matthew Wakeling, )
         Re: Raid 10 chunksize  (Scott Carey, )
          Re: Raid 10 chunksize  (Greg Smith, )
           Re: Raid 10 chunksize  (James Mansion, )
            Re: Raid 10 chunksize  (Greg Smith, )
           Re: Raid 10 chunksize  (Scott Carey, )
            Re: Raid 10 chunksize  (Greg Smith, )
           Re: Raid 10 chunksize  (Ron Mayer, )
            Re: Raid 10 chunksize  (Hannes Dorbath, )
       Re: Raid 10 chunksize  (Stef Telford, )
        Re: Raid 10 chunksize  (Stef Telford, )
         Re: Raid 10 chunksize  (Scott Carey, )
       Re: Raid 10 chunksize  (Mark Kirkwood, )
      Re: Raid 10 chunksize  (, )
       Re: Raid 10 chunksize  (, )
 Re: Raid 10 chunksize  (Greg Smith, )
  Re: Raid 10 chunksize  (, )
   Re: Raid 10 chunksize  (Greg Smith, )
   Re: Raid 10 chunksize  (Scott Carey, )

Scott Marlowe wrote:
> On Tue, Mar 24, 2009 at 7:09 PM, Mark Kirkwood <> wrote:
>
>> I'm trying to pin down some performance issues with a machine where I work,
>> we are seeing (read only) query response times blow out by an order of
>> magnitude or more at busy times. Initially we blamed autovacuum, but after a
>>  tweak of the cost_delay it is *not* the problem. Then I looked at
>> checkpoints... and altho there was some correlation with them and the query
>> response - I'm thinking that the raid chunksize may well be the issue.
>>
>
> Sounds to me like you're mostly just running out of bandwidth on your
> RAID array.  Whether or not you can tune it to run faster is the real
> issue.  This problem becomes worse as you add clients and the RAID
> array starts to thrash.  Thrashing is likely to be worse with a small
> chunk size, so that's definitely worth a look at fixing.
>
>

Yeah, I was wondering if we are maxing out the bandwidth...
>> Fortunately there is an identical DR box, so I could do a little testing.
>>
>
> Can you try changing the chunksize on the test box you're testing on
> to see if that helps?
>
>

Yes - or I am hoping to anyway (part of posting here was to collect some
outside validation for the idea). Thanks for your input!


Cheers

Mark


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