| From: | "Luke Lonergan" <llonergan(at)greenplum(dot)com> |
|---|---|
| To: | "Martijn van Oosterhout" <kleptog(at)svana(dot)org>, "Raja Agrawal" <raja(dot)agrawal(at)gmail(dot)com> |
| Cc: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Asynchronous I/O Support |
| Date: | 2006-10-15 18:11:58 |
| Message-ID: | C157C7FE.462D%llonergan@greenplum.com |
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| Lists: | pgsql-hackers |
Martijn,
On 10/15/06 10:56 AM, "Martijn van Oosterhout" <kleptog(at)svana(dot)org> wrote:
> Have enough systems actually got to the point of actually supporting
> async I/O that it's worth implementing?
I think there are enough high end applications / systems that need it at
this point.
The killer use-case we've identified is for the scattered I/O associated
with index + heap scans in Postgres. If we can issue ~5-15 I/Os in advance
when the TIDs are widely separated it has the potential to increase the I/O
speed by the number of disks in the tablespace being scanned. At this
point, that pattern will only use one disk.
- Luke
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