I had an interesting discussion with one of my geek buddies last night. Someone told him to run something against a NAS that resulted in many small input and output operations (think map reduce reads and writes) and had some issues with that ...let's just say performance issues no big company wants to experience.
In the example above the NAS was not designed for a lot of
small reads and writes.
This brings up an interesting point when considering performance of systems and determining how to architect the systems and write the software used by a particular piece of hardware. You have to understand the reads and writes your application requires and how the hardware you are running it on will handle it. For example if you are backing up data, you have large writes and minimal reads. A database or map reduce application will probably have a lot of small reads and writes.
Reading and writing data to/from disk is affected by IOPS.
IOPS = Input/Output Operations Per Second, pronounced eye-ops
http://en.wikipedia.org/wiki/IOPS
When you get an EC2 instance on AWS, for example, you can specified the IOPS. Understanding the reads and writes your application is doing will help you provision the correct amount of IOPS.
Understanding the devices in your network you are reading from and writing to will help you use the technology appropriately for a given application requirement.
