Re: Effects of setting linux block device readahead size

On Wed, Sep 10, 2008 at 9:26 AM, Scott Carey <scott(at)richrelevance(dot)com> wrote:
> How does that readahead tunable affect random reads or mixed random /
> sequential situations? In many databases, the worst case scenarios aren't
> when you have a bunch of concurrent sequential scans but when there is
> enough random read/write concurrently to slow the whole thing down to a
> crawl. How the file system behaves under this sort of concurrency
>
> I would be very interested in a mixed fio profile with a "background writer"
> doing moderate, paced random and sequential writes combined with concurrent
> sequential reads and random reads.

The data for the other fio profiles we've been using are on the wiki,
if your eyes can take the strain. We are working on presenting the
data in a more easily digestible manner. I don't think we'll add any
more fio profiles in the interest of moving on to doing some sizing
exercises with the dbt2 oltp workload. We're just going to wrap up a
couple more scenarios first and get through a couple of conference
presentations. The two conferences in particular are the Linux
Plumbers Conference, and the PostgreSQL Conference: West 08, which are
both in Portland, Oregon.

Regards,
Mark