Best Internal Hard Drive for 2010 Mac Pro

You should definitely get an SSD ≥500 GB for your boot drive. You can easily mount one on a special 2.5-in sled and place it is a drive bay. It will be ten times faster than a rotating magnetic drive, at a modest cost. Costs form about US$100 plus US$20 sled

Because your Mac Pro has four drive bays, you can use whatever Large rotating drives seem right as data drives. Absolute top speed for data drives is less important. Space is the important factor.

If you want to push the envelope a bit, you can get an SSD drive about 100 times faster than a rotating magnetic drive, and install it in a PCIe slot. (it is much faster than SATA, so it can not just go in a drive bay.) such drives require a heatsink because they are running so fast they get hot, and need more cooling. Wireheads already installed these years ago by combining parts.

OWC has some already set up (including heatsink) for you, but skip the software RAID -- it is not needed at this speed and the complexity is oppressive.

OWC 1.0TB Accelsior 4M2 PCIe M.2 NVMe SSD Adapter Card --

High-Performance PCIe M.2 NVMe SSD Adapter Card US$529

the one I cited is about US$529, and they go up with extended capacity.

Get a SSD if you can afford it based on the space you will need. I've had good luck with most brands except PNY for SSDs on Macs but who knows if that's just chance. Of the 4 PNY SSD drives I've used with Macs, 2 failed for no apparent reason.

If you'd like to use a standard HDD, possibly consider one like that is a "hybrid drive" like the FireCuda brand. These have majority traditional hard drive space on a disk but then also use a much smaller (several GBs or so) amount of space that is either solid state or RAM which acts like a buffer or cache. They definitely are an upgrade from a standard hard drive, although it still feels more like you're using a hard drive and not nearly as fast as SSD.

If you would like one that will last for years and years of heavy use, it matters less so about the brand than quality of hard drive. The manufactures do put out life expectancy statistics based on varying levels of usage. HDD often list the intended use like "for network video storage" which indicates the drive will be on 24/7 and writing large quantities of data over and over again and should for whatever reason be able to stand up to these extremes. Western Digital labels their by color like blue, black, purple, red, gold. I'd say stay away from blue or black if you're really concerned although if you have valuable data you need to be using something like a RAID anyway, as any disk can fail at any time.

Yes, the whole idea of putting an SSD in a PCIe slot is to use a VERY fast drive there and boot from it. Trying to add RAID as well precludes booting, and thereby defeats the purpose.

An SSD is your best choice these days, but make sure to get a good one since many SSDs are low end budget economy models that can be as slow (or even slower) than a hard drive when writing large amounts of data.

Also be extremely careful buying hard drives these days. The most reliable hard drives from Hitachi have been discontinued. I honestly don't know which drive is the best anymore since I don't trust either Western Digital or Seagate. Toshiba started out using the same technology as the very reliable Hitachi drives, but I've had mixed results with some of the Toshiba drives.

Seagate started having troubles many years ago (around 2011) and have only recently started producing more reliable drives according to the reports released by BackBlaze. However, we found several brand new Enterprise class drives to have bad blocks almost immediately after starting to use them. Currently I've bought some Seagate IronWolf NAS drives for a RAID storage system since Seagate drives tend to run a bit cooler. Still too early to tell how they will perform.

I've never had much luck with Western Digital hard drives over the years. Sometimes they make very good drives, but other times the drives are just awful. There is no rhyme or reason. Plus Western Digital has been caught intentionally misleading consumers with their advertising by sneaking in new technology which saves WD money (but not the consumer), but at the cost of performance. The new technology is called SMR (Shingled Magnet Recording) which makes writing to a hard drive extremely slow! WD put this technology into drives where performance does matter without telling anyone about the change. You want to stay away from any hard drive using SMR except for very limited use cases.

Stay away from Desktop grade drives especially in a Mac Pro where you have multiple drive bays and lots of vibration. A NAS drive is better suited and should be more reliable. Be careful navigating the WD NAS drives though since they have three different variations on their Red NAS drive series plus there are some early WD Red NAS drives which secretly use SMR technology but are not listed as such (you must look at the product number to know which models use SMR). The best WD Red NAS drive is the Pro series which has a spindle speed of 7,200rpm. Stay away from the standard Red NAS drive as it is definitely using the SMR technology. The Red Plus (?) I believe is a variable speed drive up to 5,400 (maybe 5,900) rpms. Seagate has said they are not going to use the SMR technology in their NAS drives. I am unsure about Toshiba's product line as I haven't been purchasing too many hard drives recently.

You must be extremely careful buying hard drives (not enough competition) and equally careful purchasing SSDs as well (so many low end budget SSDs since consumers care more about saving money than realizing how poorly these budget SSDs really perform). The choice between a WD Red Pro NAS, Seagate Iron Wolf NAS, or a Toshiba NAS hard drive is about even. The Crucial MX500 series is currently a good middle ground on price/performance and reliability. OWC Mercury Electra SSDs are Ok, but I'm not a fan of them. Samsung EVO and PRO SSDs are much more expensive and unfortunately new models are starting to use TLC and even QLC NAND which is not as good (but allows for larger cheaper drives). Some Samsung EVO models have had compatibility issues with some Macs (not sure which models).