> > Yup, that would be the scenario where it helps (provided that you
have
> > a smart disk or a disk array and an intelligent OS aio
implementation).
> > It would be used to fetch the data pages pointed at from an index
> > leaf, or the next level index pages.
> > We measured the IO bandwidth difference on Windows with EMC as
beeing
> > nearly proportional to parallel outstanding requests up to at least
>
> Measured it using what? I was under the impression only one
> proof-of-implementation existed, and that the scenarios and
> configuration of the person who wrote it, did not show
> significant improvement.
IIRC the configuration of that test was not suitable to show any
benefit.
Minimum requirements to show improvement are:
- very few active sessions (typically less than number of disks)
- a table that spans multiple disks (typically on a stripe set)
(or one intelligent scsi disk)
- only random disk access plans
> You have PostgreSQL on Windows with EMC with async I/O
> support to test with?
No, sorry. Was a MaxDB issue.
Andreas
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