Since replacing my 5K iMac with a new iMac Pro, I’m a huge fan of Thunderbolt 3 for maximum throughput. Meet the TerraMaster D5 DAS (Direct Access Storage). You buy this enclosure empty, and add your own drives. I installed five 8 TB Western Digital “Red” drives inside. They’re 3½” SATA drives, not SSDs. Why? Well, because the cost per terabyte is less than $59 and this enclosure puts a super fast interface on them to make up the difference.
I got the enclosure on an Amazon “Lightning Deal” for $639, where the regular price was $799. Each hard drive was $249. So for a total investment of $1,884 I got 40 TB of total storage, which should meet my demanding video production needs for the foreseeable future.
This is a RAID controller, so I configured it using RAID-5 mode. That means out of 40 TB of total storage, the controller will read and write data across all five drives at once to maximize access speed and redundancy. So while the effective available storage is reduced to 32 TB now, that means any one drive can go bad and everything keeps working until that drive can be replaced. Once replaced, the controller rebuilds the array and all is good again.
I’ve been using a 16 TB NAS (Networked Attached Server) for a couple years, so there were a number of problems to solve:
- Access speed to and from my NAS was too slow over Gigabit Ethernet. I was spending way too much time waiting for large files to copy. It was also doubling as an FTP server for my security cameras, which meant that it was very painful to browse those files quickly or efficiently.
- I was close to maxing out the space on my NAS. At first I used it in RAID-1 (mirrored) mode, which cut its available space down to 8 TB. I later switched it to RAID-0 (striped) and then to JBOD (just a bunch of discs) mode to gain access to all 16 TB, but of course that left me nervous about a potential drive failure.
- My NAS was not encrypted or backed up. Not good.
Configuring the TerraMaster took some trial-and-error, given that its UI is typical Chinese garbage. My goal was to strike the best balance between performance, convenience and security — on a volume-by-volume basis.
The first major decision you have to make is the base format. On a modern Mac, your main choices are “MacOS Extended (Journaled)” or “APFS.” You get the option to add “Encrypted” to either choice, but that’s where things get confusing.
Apple’s Time Machine, love it or hate it, is not yet compatible with APFS. And worse, Time Machine does not play nice with encryption. So after a few false starts, here’s what I wound up doing:
- I made a dedicated 2 TB partition using Disk Utility. I formatted that partition using MacOS Extended (Journaled, Encrypted) and named it “Time Machine.”
- I formatted the remaining 30 TB partition as APFS, unencrypted.
- Within that 30 TB partition, I created a few different volumes. APFS volumes get dynamically resized, so you don’t have to commit to those sizes the same way you would for partitions. I chose Encrypted for some of those volumes, and left others unencrypted.
Why? Because encryption incurs a performance hit and I don’t need that much security for everything I’ll use this file server for. And plus, you can always add, rename or resize volumes later in Disk Utility without losing data. And you can replace them as long as you have a way to back them up first.
Using the Blackmagic Disk Speed Test app, here are some typical results:
- Write/Read to unencrypted portions of DAS: 515/755 MB/s
- Write/Read to encrypted APFS volumes on DAS: 475/725 MB/s
- Write/Read to encrypted Time Machine partition: 375/375 MB/s
Now by comparison, I had some cool 1 TB SanDisk Extreme SSDs connected via USB 3.1. They cost $199 each. Those SSDs yield around 450/500 MB/s on my iMac Pro. So you can see how these 8 TB SATA drives are comparable to 1 TB SSDs at a fraction of the cost: $59 per terabyte versus $199 per terabyte — just not nearly as portable.
So yeah, I’m pretty happy with this solution. Especially considering the biggest 2½” internal SSDs you can buy are 4 TB. And they still cost around $699. Using five of those would yield only 16 TB and bring the total investment up to around $4,134 or $258 per terabyte. That’s 4.4X more expensive than these traditional mechanical drives. And by the time these start failing, SSDs will be much cheaper replacements.
Now there’s some learning to share, for those of you thinking about (or struggling with) the same setup. Here are some lessons I learned:
- Apple’s System Utility teams are sadists, and there’s a special place in Hell for them. Not just Disk Utility, but other essential tools like Migration Assistant, Time Machine and AirPort Utility. Their biggest sin is not providing actionable error messages.
- Make sure you understand the limitations of Apple’s file formats up front. And no, they aren’t very well documented.
- Time Machine cannot write to an APFS drive, period. It’ll warn you that the disk is not the right format. Sadists generally don’t want you to know about their shortcomings.
- You can partition a drive (or an entire RAID array) first, separating the MacOS Extended (Journaled) portion from APFS. And then you’ll have the best of both worlds — as long as you pick the right amount of space for Time Machine to grow over time up to a limit. In my case, I chose 2X the size of my iMac Pro’s internal SSD.
- Be sure to encrypt Time Machine’s partition first, using Disk Utility. Then add that volume as a Backup Disk in Time Machine’s UI. Tell Time Machine to use “Encrypt backups” again at this point, even though it doesn’t make any sense.
- If you do it this way, Time Machine will make its initial backup in around 90 minutes for a 1 TB system. And then it’ll all be done. Yes, it’s inexcusable that Apple continues to ship versions of Time Machine without proper guidance in its UI, when clearly they know about these pitfalls.
- If you don’t do it this way, Time Machine will make its initial backup very quickly, but it will spend days encrypting it separately. That is no exaggeration. This is a major flaw in Time Machine’s algorithm. That progress indicator will be stuck at around 13% for hours and hours while your drive(s) thrash.
- Know that if you’re ever tempted to uncheck Time Machine’s “Back Up Automatically” checkbox, it will abort any backup in progress without warning and it’ll have to start over. Yep, like I said: Sadists. That button used to be titled something like Start/Stop Backup, which reflected the fact that this control is more of an action than a preference. But the lack of a confirmation dialog is absolutely negligent on Apple’s part.