Mac Pro Storage

Booting Your Mac

Even the very last year of Mac Pro tower (2012) only supported SATA 2 connections for hard drives, which was slow at the time and is even slower today. Not to worry though because you can install a much faster PCIe card hosting NRAM storage using an OWC Accelsior E2 or OWC Mercury Accelsior Pro Q for your system volume and applications, however these are getting difficult to find but start at around $200 on eBay going up to over $1000 for Pro Q. The Accelsior E2 supports 820MB/s read & writes while the Pro 2 is much faster with sustained speeds of 1,293MB/s. Neither are still being made which means you need to troll eBay looking for a good quality second hand card.

OwC also sells a couple of other PCIe cards that you might like to consider that are all faster than the built in SATA 2. The OWC Mercury Accelsior S is a PCIe card that allows you to mount a 3G or 6G SSD and supports sustained speeds of 550MB/s. It sells for just under $50 on the macsales OWC's web site.

You could also use an OWCMercury AccelsiorM mSATA PCIe Controller which works with any standard mSATA SSD. The AccelsiorM mSATA supports a respectable 380MB/s read & write performance and sells on for $19. 
New to the OWC Lineup and much faster (not that your Mac will benefit from all of that speed due to the older PCIe bus speed) is the OWC Accelsior 1M2 a PCIe 4.0 card supporting M.2. NVMe Storage. The card can be purchsed in 240GB to 8TB capacity or you can buy the empty card for $29 and purchase your own single SSD M-key in 2230, 2242, 2260, 2280, or 22110 lengths. The 1M2 supports speeds of up to 3,200 MB/s.
Faster again is the OWC Accelsior 4M2 with a read speed of up to 6,000 MB/s using built in RAID0 across 4 SSD M-key slots. OWC sells this in 0GB to 32TB configuration.
Topping out the lineup is the new OWC Accelsior 8M2 with a read speed of 12,000 MB/s or 26,000 MB/s using PCI Gen 4 storage.

The OWC Accelsior lineup supports booting a mac whereas other PCIe M2 drive solutions may need their firmware modifying. If you purchased a used Accelsior E2 from Ebay you may need to update the firmware which can be found on OWC's web site. Careful there are several different models.

The nice thing about booting your OS and applications from one of these cards is that you can then use the standard Mac SATA 2 drive bays for storage using inexpensive 3.5" drives. You can if you want, also use the 5.25" CD/DVD bays for storage as well with the right adapter.

Mercury Accelsior E2

OWC Accelsior S

Mercury AccelsiorM mSATA PCIe Controller

OWC Accelsior 1M2
OWC Accelsior 4M2

 OWC Accelsior 8M2


All Mac pro towers are designed with four 3.5" drive bays and 4 caddies. Mac Pro 1,1, 1,2 and 1,3 have different caddies to the later 4,1 and 5,1 models so they are not interchangeable. Factory caddies support the old hard drive screw layout and will hold most drives up to 4TB. From 6TB drives onwards the base screw layout changed so if you want some large storage then you will need to invest in replacement caddies from OWC. I believe these are only available for 4,1 and 5,1 models.

OWC Replacement Caddies

With the right caddies, you can install up to four 8TB, and possibly 10TB and 12TB modern SATA 3 drives in your Mac Pro and software stripe (RAID0) or mirror (RAID1) them for a capacity of up to 48TB and beyond. That should be more than enough for most people's data needs even if you have hundreds of movies and thousands of tunes. Of course you will only be able to access these drives at SATA II speeds using the native SATA controller but that's enough for most people's data storage needs. Thermal capacity of the cheese-grater case is good but I usually use 5,400rpm NAS drives to keep the heat down.

The Mac Pro 5,1 only supports hard drives that run or emulate 512 byte block size.

Since 2011, many manufacturers began to offer hard drives with a physical block size of 4096 bytes (4K for short). These are also referred to as "Advanced Format" drives and will often carry the Advanced Format 'emulation logo' on their label. This is a major shift from the 512 byte physical block size used for many years prior to 2011. The main benefits are the potential for greater capacities and improved reliability, as well as some performance gains.

However, many existing operating systems, applications, devices, and computers were designed to work specifically with drives that provide 512 byte block sizes. This includes the Mac Pro 5,1 and most OWC drive enclosures - a favorite with Mac users. 

To ease the transition to 4K native drives (4Kn for short), drive manufacturers have integrated 512 byte emulation technology (or 512e for short). This enables drives with physical block sizes of 4096 bytes to work with computers, systems, applications, and devices designed for use with drives that have 512 byte physical blocks. Some new drives don't support this including the new helium filled enterprise drives from WD. In other words, check before you purchase!

If you want to run RAID5 across your internal drive basy, you will need to add a RAID card but beware that the Apple RAID card has a maximum addressable drive size of 2.2TB for each drive which means you are wasting space if you can only address part of each drive. A number of third party RAID cards solve this and the SATA2 limitation and some even support SAS rather than SATA3. Bear in mind they are still pretty expensive and you need something that will work with macOS.

If you are after some cheap used storage for the inside of your Mac Pro, you can pick up used Enterprise SAS drives on Ebay for pennies. These fit the factory caddies but you need an Apple RAID card to address them. Bear in mind the 2.2TB per drive limitation so 3TB drives are great. One thing I found with mine is that the drives I purchased take a bit longer to spin-up than consumer hard drives so you may get a 'Volume Missing' message from a power-on cold boot - just reboot without powering off and it will fix the problem. My systems stay on all the time anyway so its not a problem for me, but if you are the kind of person that powers off their system every night then you are probably better off with consumer 5,400rpm eco green drives or cloud storage.

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