Re: Amazon EC2 CPU Utilization

John R Pierce <pierce@hogranch.com>

From: John R Pierce <pierce@hogranch.com>
To: Jim Mlodgenski <jimmy76@gmail.com>
Cc: Mike Bresnahan <mike.bresnahan@bestbuy.com>, pgsql-general@postgresql.org
Date: 2010-01-27T22:55:06Z
Lists: pgsql-bugs, pgsql-general
> I have seen behavior like this in the past on EC2. I believe your 
> bottleneck may be pulling the data out of cache. I benchmarked this a 
> while back and found that memory speeds are not much faster than disk 
> speeds on EC2. I am not sure if that is true of Xen in general or if 
> its just limited to the cloud.  

that doesn't make much sense.

more likely, he's disk IO bound, but hard to say as that iostat output 
only showed a couple 2 second slices of work.   the first output, which 
shows average since system startup, seems to show the system has had 
relatively high average wait times of 100ms on the average, yet the 
samples below only show 0, 2, 3mS await.