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Date: Sat, 20 Nov 2010 11:16:42 +0100
Message-ID: <AANLkTimC_VVWvg46MZBdXPtMPms0uHiUmLNPkNOhDR+F@mail.gmail.com>
Subject: Re: How to achieve sustained disk performance of 1.25 GB
	write for 5 mins
From: Dimitri <dimitrik.fr@gmail.com>
To: Greg Smith <greg@2ndquadrant.com>
Cc: Eric Comeau <Eric.Comeau@signiant.com>,
 Merlin Moncure <mmoncure@gmail.com>,
	pgsql-performance@postgresql.org
Content-Type: text/plain; charset=ISO-8859-1

You may also try the Sun's F5100 (flash storage array) - you may
easily get 700 MB/s just with a single I/O stream (single process), so
just with 2 streams you'll get your throughput.. - The array has 2TB
total space and max throughput should be around 4GB/s..

Rgds,
-Dimitri


On 11/18/10, Greg Smith <greg@2ndquadrant.com> wrote:
> Eric Comeau wrote:
>> Ideally 1 large file, but it may have to be multiple. We find that if
>> we send multiple files it just causes the disk to thrash more so we
>> get better throughput by sending one large file.
>
> If it's really one disk, sure.  The problem you're facing is that your
> typical drive controller is going to top out at somewhere between 300 -
> 500MB/s of sequential writes before it becomes the bottleneck.  Above
> somewhere between 6 and 10 drives attached to one controller on current
> hardware, adding more to a RAID-0 volume only increases the ability to
> handle seeks quickly.  If you want to try and do this with traditional
> hard drives, I'd guess you'd need 3 controllers with at least 4
> short-stroked drives attached to each to have any hope of hitting
> 1.25GB/s.  Once you do that, you'll run into CPU time as the next
> bottleneck.  At that point, you'll probably need one CPU per controller,
> all writing out at once, to keep up with your target.
>
> The only popular hardware design that comes to mind aimed at this sort
> of thing was Sun's "Thumper" design, most recently seen in the Sun Fire
> X4540.  That put 8 controllers with 6 disks attached to each, claiming
> "demonstrated up to 2 GB/sec from disk to network".  It will take a
> design like that, running across multiple controllers, to get what
> you're looking for on the disk side--presuming everything else keeps up.
>
> One of the big SSD-on-PCI-e designs mentioned here already may very well
> end up being a better choice for you here though, as those aren't going
> to require quite as much hardware all get wired up.
>
> --
> Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
> PostgreSQL Training, Services and Support        www.2ndQuadrant.us
> "PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books
>
>