Upgrading SSD Boot Drive: USABLE Capacity Increase Is Even Better Than It Seems
Get OWC Aura and Aura Pro SSDs at MacSales.com (480GB and 960GB).
Following up on my review of the OWC Aura SSD upgrade for MacBook Air and MacBook Pro Retina, the question of value arises: cost is a factor of course, but also the actual gains in usable storage.
When considering an upgrade of the internal SSD, the right comparison is not the nominal SSD capacities, but rather the increase in usable storage. That is, baseline storage requirements determine the actual increase in usable storage.
Consider as shown at right a minimal system: fresh install, and the only extra app of Adobe Photoshop, with no user data at all. With this very basic system, the actual usable capacity difference is 9.4X, not the 8X implied by the SSD capacity (120GB vs 960GB).
But for most users, a minimal system with various apps is likely to be closer to 60GB*, which makes the ratio (960-60)/(120-60) = 900/60 = 15X. In other words, a 1TB (960GB) SSD upgrade from 128GB offers an 15X increase in usable capacity, even though the SSDs are only 8X different in size.
That ratio diminishes when upgrading from a 256GB or 512GB SSD but is still highly favorable. Moreover, some users have fairly demanding baseline storage requirements.
Lloyd’s laptop situation
Lloyd’s own real-world travel requirements for photography require working web sites and git repositories on the MacBook Pro Retina while traveling.
Along with system and apps, these requirements eat up 290GB of a 512GB (499GB) SSD, leaving only 209GB of usable storage.
Thus for Lloyd’s particular usage, upgrading from a 512GB (499GB) Apple SSD to a 1TB (960GB) SSD represents an increase in usable capacity of (499-290)/(960-290) = 670/209 = 3.2X, a far greater benefit than the nominal 2X capacity difference.
In the real world, usable capacity gains are all that matter—not the nominal capacity. So figure out your own situation and thus the real gains in usable storage, your “room to roam”.
* Minimum capacity for a system involves the need for application installations, virtual memory swap space, some unused space to avoid show-stopper system halts and poor performance, etc. A minimum of 20GB free space is advised to avoid headaches.