Well, I don't think you got ripped off, I'd say that's a good price for that drive, if it's not too old.
It's not obsolete, it's a hard drive mainly used in file servers and such.
The drive uses an interface called SCSI. Unfortunately, SCSI cannot connect directly to the P5K, or really any motherboard on the market. To use the drive you would have to buy a separate RAID controller card, that has SCSI ports on it. This would be installed on one of the PCI slots, and the hard drive would connect to the card.
@OP: I agree, sell it and get a SATA drive. Be careful, if the drive is stolen, you can get burned for theft or receiving/ trafficking in stolen goods. HDDs have serial numbers, and I would imagine most companies register them.
That Hard Drive retails anywhere from $259-$450.
So....even if you have to buy a SCSI controller, I wouldn't say the OP got ripped off.
However, you could have bought a 10,000rpm Raptor for the price of the drive and controller, would have plugged right into your motherboard, and for all practical desktop/home build purposes would have performed just as well.
I believe it a 80 pins (SCA) too, right (not 68 pins)? 80 pins is a combined power to the 68 pins. If you buy a SCSI card, you must also add an adapter to convert 80 to 68. The previous post is an adapter for 68 pins. 80 are also normally in a cage for HotSwappable drive in a RAID5 configuration.
For the drive, 15K are the best and very expensive. Really for server environment.
By the way...any SCSI controller from Ultra2 on up will work with that drive, however be aware that the data speed will be governed by the controller you choose even while the differences are neglible. Know also, that some SCSI controllers do not come with a bootable BIOS so be careful in your selection if you intend to boot from that drive. You will need an 80 to 68 pin SCSI adapter and a 68 pin cable.
One of the great things about SCSI is the number of disks one can run from one controller. I have one setup with 4 10K drives and another with three.
I don't know where you guys are getting your prices, but on eBay you can find a used SCSI card for under $10, sometimes even with RAID. I scored a dual channel RAID card with 256meg cache for $20 on there a few months back.
Also, the adapter typically costs more around $2-3, he can easily get the card and adapter for under $20.
As far as the drive, that is an insanely cheap price, I'm gonna have to agree with the poster that said it was likely stolen.
You will get rather uniform performance even with native controllers.
Adequate case cooling is always a good idea, but especially so if you are using SCSI as they (10k and 15k drives) are typically referred to as "space heaters". Anything that spins that fast is bound to generate some heat.
Web servers do not really "need" such high speed drives unless you have a great many simultaneous hits. SCSI is most noted for it's sustained tranfer speed. Almost any modern hard drive will perform well for modest service.