ST31000340NS vs ST31000340AS

NS drives are enterprise models with slightly higher MTBF numbers. Probably identical drives otherwise from what I could tell.

"Slightly higher" is about 60%... the seagate website says 750,000 hrs MTBF with a 0.34% annual failure rate for the AS versus 1,200,000 hrs and 0.73% for the NS. Other minor differences, but essentially the same drive.

The drives have exactly the same specs except MTBF. What could possibly be the physical difference between them? They also both probably have the same warranty, which is usually 5 years. Note that 750,000 hours is about 85 YEARS. Nuff said.

I have tried both drive models in a datacenter environment. They both fail about the same. For piece of mind and to be right, I still buy NS model for datacenter servers, even though I didn't notice the difference.

Don't forget - part of figuring MTBF includes the expected working environment. A server farm is usually expected to be much more hardware friendly than being stuck under desk in the corner of the living room. So, as far as MTBF is concerned, it could be smoke & mirrors, or there may actually be some difference in the operating parameters as the drive comes from the mfr.

I've been springing for the ES drives lately. It's worth the possible extra life out of them. I would suspect there are manufacturing differences in them. If they are rating them to work longer without error I would think there is some testing and or differences even though on paper they are pretty much identical.

Two other differences between an AS and an NS series drives

Non-recoverable error rate (1 per 10^15 for the NS, 1 per 10^14 for the AS)

Rotational vibration tolerances are higher on the NS

The rotational vibration tolerance is prob. the big one for multi-drive servers esp. for those that don't have any individual drive isolation (i.e. drives are just screwed into a disk caddy and the disk caddy slides in on metal rails). Get 4-8 drives in that kind of arrangement and the vibration that is caused by head movements of the drives will cause rapid failure in the drives. With the AS class drives in a 8 disk server chassis we can get about 12 months before we start seeing drive failures.

Craig

I was also told by Seagate the the NS drives are designed to run 24/7 and the AS drives are designed to run about 8 hours a day.

The NS drives also have server-tuned firmware and cache algorithms.

The NS have a vibration sensor, which accounts for the greater vibration tolerance and the MTBF improvement.

I bought the NS drives for my NAS, it was worth the extra dollars for what I believe are better drives. The two NS drives run 24/7 and have been running for six months now, without issues.

NS v AS

I ment the ES.2 Drives. Which are the NS model number. Sorry

I have purchased two NS drives , both used in a low use environment. One failed after 4 weeks, the second after another 3 months. I have no experience with the AS drives, but I would not touch the NS again.

The NS drives have a five year warranty, vs. a three year warranty for the AS drives.
That corresponds roughly to the comparative MTBF: 1,200K hrs. for the NS vs. 750K hrs. for the AS.
I couldn't find the warranty for the AS drives at seagate.com, but Amazon has it here:
http://www.amazon.com/Seagate-Barracuda-7200RPM-Interna...

The NS drives are much more expensive than the corresponding AS drives, from what I have seen.

A 1TB NS drive weighs 672g vs. 622g for a 1TB AS drive.

The load rating for the NS is 3w vs. 2w for the AS.

The drives are not the same. I wouldn't try to use the PCB's interchangeably between the NS and the AS. But you might, and you might even get away with it.