Apple laptops including Retina MacBook Pro and all but the first MacBook Air models rely solely on SSDs for internal storage. Over the years, the Cupertino giant kept on slimming the design to the point that even a 1.8″ hard drive was too bulky. Apple never adopted mSATA or later M.2 form factor, and kept on using custom form factors and pinouts. This has resulted in a smaller third party market for upgrades.
Not many companies have produced SSDs in Apple-specific form factors other than Other World Computing (OWC) and Transcend. Transcend has mostly used Silicon Motion controllers while OWC relied on SandForce controllers, but until now their offerings have been limited to SATA-based SSDs.
In 2013, Apple switched to PCIe-based interfaces from SSDs for their notebooks and used drives supplied by Toshiba, SanDisk, and Samsung. Finally, OWC has come with a compatible replacement and released it as part of their Aura SSD product line.
The OWC Aura PCIe SSD makes use of AHCI protocol just like the Apple originals; Apple so far only supports and uses NVMe on the Retina MacBook that doesn’t have a removable SSD. This requirement of using AHCI instead of NVMe limited OWC’s choices for SSD controller. While, Apple was able to convince Samsung in making SM951 in a custom form factor, it failed to do so with OWC. Marvell has been shipping several AHCI-compatible PCIe SSD controllers, but their business model lies around just the selling part and leave it up to the customer to write their own firmware or license from a third party, either of which is a substantial up-front expense.
Therefore, to keep the costs in check, OWC went ahead with using a Marvell 9230 SATA RAID controller and a pair of Silicon Motion SM2256 SATA SSD controllers for PCIe Aura SSD instead of a native PCIe SSD controller. The Marvel 9230 comes with PCIe 2.0 x2 host interface, so the PCIe Aura SSD has the potential to outperform SATA SSDs but won’t be able to approach the peak transfer rates of the recent Samsung SM951-based Apple originals. The Silicon Motion SM2256 controllers mean the PCIe Aura SSD is almost certainly using TLC flash, which is less expensive but also performs worse and draws more power than MLC flash. Unfortunately, the PCIe Aura SSD’s RAID design does not support passing through TRIM commands nor retrieving SMART information from the individual SSD controllers.
If we go by OWC’s measurements of the first PCIe SSDs Apple used back in 2013, the Aura SSD’s peak performance is slightly better than the slowest 128GB SanDisk/Marvell drive, but without TRIM, the Aura’s write performance advantage could easily disappear over time. Hence, capacity is the only strongest selling point for PCIe Aura SSD.
For example, Apple can configure the MacBook Air up to 512GB of storage, but the Aura SSD can provide up to 960GB storage. Apple memory based upgrades are pretty steep with $200 to upgrade from 128GB to 256GB, another $300 to move up to 512GB, and another $500 to move up to 1TB for the MacBook Pro. Whereas OWC’s Aura comes at $347.99 for 480GB and $597.99 hence making it cheaper than Apple’s own solution.
You can buy The Aura SSD as a bare drive or an upgrade kit that includes the necessary screwdrivers to install the SSD and a USB 3.0 enclosure to facilitate data migration. It’s expected to start shipping in late March.