On 01/07/15 17:37, Amit Kapila wrote:
On Tue, Jun 30, 2015 at 4:00 AM, Jeff Davis <pg...@j-davis.com
<mailto:pg...@j-davis.com>> wrote:
>
> [Jumping in without catching up on entire thread.
[...]
.
> 2. Where is the speedup coming from? How much of it is CPU and IO
> overlapping (i.e. not leaving disk or CPU idle while the other is
> working), and how much from the CPU parallelism? I know this is
> difficult to answer rigorously, but it would be nice to have some
> breakdown even if for a specific machine.
>
Yes, you are right and we have done quite some testing (on the hardware
available) with this patch (with different approaches) to see how much
difference it creates for IO and CPU, with respect to IO we have found
that it doesn't help much [1], though it helps when the data is cached
and there are really good benefits in terms of CPU [2].
[...]
I assume your answer refers to a table on one spindle of spinning rust.
QUESTIONS:
1. what about I/O using an SSD?
2. what if the table is in a RAID array (of various types), would
having the table spread over multiple spindles help?
Cheers,
Gavin
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