Question 1

Is this a 9½ mm drive?

Accepted Answer

NO.  This drive is more like 14.7mm thick.
It has the normal "footprint" (and connector location, relative to mounting plane) of a 2.5" SATA HDD, but it will probably not fit most notebooks.  It does not possibly fit into my Lenovo, nor my HP.  It could fit if you have a double-height bay, or use an adapter to fit a 3.5" or 5.25" bay.  I am using this drive for backup archives and it lives in my safe, so I don't care much about the form factor.
I will also note that it can not be used with a simple port-powered USB-SATA adapter, because apparently it relies on standard/old-school 12V as well as a 5V supply.  I have a USB adapter that has its own plug-in power supply which makes it a non-issue.
For real-time use of this drive, you are probably looking at a powered enclosure for a larger form factor, a desktop PC, or a server chassis with a 2.5" drive bay adapter.
Given my minimal usage profile of it, I can not comment on longevity or performance.  All I know is I "rsync"ed about 460GB onto it without concern for speed, and everything checks out perfectly.
I hope this is helpful; I know it exceeds your question but I thought I'd tell you all I know about it.

Question 2

People say this won't get powered by a laptop. What about a tower with a 3.5" adapter?

Accepted Answer

In spades.  That's what I'm doing with it.  I have an HP mediacenter tower (running Linux so it doesn't matter that it is old), with IDE AND SATA ports in it (I suppose that makes it about 10 years old - it was a hand-me-down)...  It's hooked up to a Molex (old-school whitish power connectors) plug in my ATX harness using a SATA power adapter.  (The data connection is simply made to an available SATA port with a standard SATA data cable.)  The Molex connectors provide 5V, 12V and 2 grounds, so there is no 3.3V (typically orange wire in SATA power connector).  The drive works since (like many SATA drives) it does not require 3.3V.  It DOES require 12V and I'm guessing laptops don't supply that (in addition to the fact that the drive is too thick to fit any laptop bay of which I am aware).  It's 2.5" so it just "looks" like a laptop drive.  A chassis adapter (for a 2.5" drive in 3.5" bay) works perfectly to make it a 3.5" one (frankly I personally know of no other way to install it).  If your chassis has SATA style power connectors, you're good to go, with no need for an adapter.

Brand	Seagate
Series	Constellation
Model	ST9500530NS
Packaging	Bare Drive

Interface	SATA 3.0Gb/s
Capacity	500GB
Cache	32MB
Average Latency	4.16ms
RPM	7200 RPM

Seagate Constellation ST9500530NS 500GB 7200 RPM 32MB Cache SATA 3.0Gb/s 2.5" Internal Enterprise-class Hard Drive Bare Drive

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Item#: N82E16822148493