Re: PG-related ACM Article: "The Pathologies of Big Data"

Well, there is CPU overhead for reading postgres pages and tuples. On a
disk subsystem that gets 1GB/sec sequential reads, I can't get more than
about 700MB/sec of I/O and on a select count(*) query on very large tables
with large rows (600 bytes) and its closer to 300MB/sec if the rows are
smaller (75 bytes). In both cases it is CPU bound with little i/o wait and
disk utilization under 65% in iostat.

I also get over 13GB/sec to RAM from a single thread (Nehalem processor).

I don't see how on any recent hardware, random access to RAM is slower than
sequential from disk. RAM access, random or not, is measured in GB/sec...

On 8/7/09 5:42 PM, "Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com> wrote:

> Oh I just noticed his graphic is "values per second" but he had
> originally said they were 16 bit values. Even if they were 32 or 64
> bit values, I'd expect way more than what he's getting there.
>
> On Fri, Aug 7, 2009 at 6:40 PM, Scott Marlowe<scott(dot)marlowe(at)gmail(dot)com> wrote:
>> Well, from the article, I got the feeling he never showed up here on
>> the list to ask for help, and he just assumed he knew enough about
>> postgresql to say it couldn't scale well.  I just checked the
>> archives, and his name doesn't show up.
>>
>> When you look at his slides, this one makes we wonder about a few points:
>>
>> http://deliveryimages.acm.org/10.1145/1540000/1536632/figs/f3.jpg
>>
>
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