Re: High load and iowait but no disk access

Поиск
Список
Период
Сортировка
От Tom Lane
Тема Re: High load and iowait but no disk access
Дата
Msg-id 22550.1125419342@sss.pgh.pa.us
обсуждение исходный текст
Ответ на Re: High load and iowait but no disk access  (Rémy Beaumont <remyb@medrium.com>)
Ответы Re: High load and iowait but no disk access  (Rémy Beaumont <remyb@medrium.com>)
Список pgsql-performance
=?ISO-8859-1?Q?R=E9my_Beaumont?= <remyb@medrium.com> writes:
> On 30-Aug-05, at 12:15, Tom Lane wrote:
>> I know zip about NetApps, but doesn't the 8th column indicate pretty
>> steady disk reads?

> Yes, but they are very low.

Sure, but that's more or less what you'd expect if the thing is randomly
seeking all over the disk :-(.  Just because it's a NetApp doesn't mean
it's got zero seek time.

You did not say what sort of query this is, but I gather that it's doing
an indexscan on a table that is not at all in index order.  Possible
solutions involve reverting to a seqscan (have you forced the planner to
choose an indexscan here, either directly or by lowering random_page_cost?)
or CLUSTERing the table by the index (which would need to be repeated
periodically, so it's not a great answer).

            regards, tom lane

В списке pgsql-performance по дате отправления:

Предыдущее
От: Tom Lane
Дата:
Сообщение: Re: High load and iowait but no disk access
Следующее
От: Rémy Beaumont
Дата:
Сообщение: Re: High load and iowait but no disk access