When considering a new iMac Pro for your desk, you have several factors worth weighing as you configure it: number of processor cores, RAM, video cards, and whether you should get all the space gray accessories, of course.
But there's one more feature worth considering when building your iMac Pro: your internal storage space.
All iMac Pro options come with NVMe-based SSD (solid-state drive) storage — there's no Fusion Drive model to be found here. SSD storage is both faster and sturdier than a traditional spinning-disc hard drive, and allows you to access your projects faster, boot up more quickly, and run through massive number-crunching at full speed.
Like its fellow upgrades, your SSD isn't user accessible on the iMac Pro: What you buy at launch is what you get forever.
That said, it's a lot easier to augment your storage space than your internal processor or RAM: The iMac Pro comes with 4 Thunderbolt 3/USB-C ports, which support connecting multiple RAID arrays; these are systems made up of multiple hard drives, and can be used either to help support network storage or as direct add-ons to your Mac.
You'll also find a single 10Gb Nbase-T Ethernet port, which allows users to connect directly to their network's attached storage (NAS).
Who should get the 1TB SSD?
The 1TB SSD ships as the iMac Pro's standard $4999 configuration; its solid-state storage should provide fast boot times for the system itself, as well as speedy local storage for files in progress.
Unlike most of the iMac Pro's optional upgrades, the 1TB SSD standard is a more reasonable base for most pro users. Thunderbolt 3 RAID enclosures have brought external storage options closer to the speed of internal drives, and also made backing up your system an easier prospect.
Users who spend a lot of time working with external storage should be fine with the 1TB standard drive, as well as those who work via network storage.
If you instead need ultimate speed for your files, you might want to look at the 2TB or 4TB SSD.
Who should get the 2TB SSD?
For $800, you can double your Mac's on-board SSD storage to 2TB; this is the same price as the 64GB RAM or 10-core CPU upgrade.
Were you to look for a portable USB-C SSD in the same storage range, you'd find prices ranging from $800-$2000; Thunderbolt 2 RAID systems run around $1000 (no pre-packaged Thunderbolt 3 SSD RAID systems currently exist on the market). As such, if you need the storage and the speed an SSD provides, it may well be cheaper to opt in to Apple's upgrade.
Of course, the bigger your drive, the bigger your backup system. There are various ways to back up your Mac, including traditional spinning-platter hard drives; for instance, you can buy a 12TB Thunderbolt 3 RAID drive for $800.
If you rely on SSD speed and frequently work locally on big projects, the 2TB SSD may be a valuable upgrade; if speed is less of a concern than overall storage, consider sticking with 1TB and buying an external Thunderbolt 3 RAID array with spinning-platter disks, instead.
Who should get the 4TB SSD?
The 4TB SSD upgrade will cost prospective iMac Pro buyers a whopping $2800 to upgrade, and for good reason: It's one of the largest, fastest SSDs you can buy in a Mac. You can get external SSD storage at a slight discount (VectoTech offers a portable 4TB SSD for a mere $1600), but even USB 3.1 speeds won't compare to a built-in system.
Why would you want to spend more than half the cost of a baseline iMac Pro on hard drive space? Simple: You need high-speed local storage for space-hogging projects. 8K video and rendering files, VFX, VR work, complex computations — all of these require huge amounts of storage, and saving them locally makes the process of editing, effects work, and the like that much easier.
If you work in an industry where speed and space are musts, the 4TB upgrade can help get what you need from your Mac. (It's worth noting, however, that if you're opting for the 4TB hard drive upgrade, you may also want to consider upgrading your processor, RAM, and graphics card to match.)
If you can manage instead with external drives and NAS, save yourself the cash and opt for one of the iMac Pro's other upgrades.
What iMac Pro SSD size would you get?
Considering an iMac Pro? Which SSD size would you opt for? Let us know in the comments.
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Serenity was formerly the Managing Editor at iMore, and now works for Apple. She's been talking, writing about, and tinkering with Apple products since she was old enough to double-click. In her spare time, she sketches, sings, and in her secret superhero life, plays roller derby. Follow her on Twitter @settern.