OWC Introduces SSD Upgrade for MacBook Pro and MacBook Air PCIe SSDs

Apple's Retina MacBook Pro and all but the earliest MacBook Air models have relied solely on SSDs for internal storage, as Apple slimmed down the designs to the point that even a 1.8" hard drive was too bulky. Rather than adopt the mSATA or later M.2 form factor, Apple's SSDs have used custom form factors and pinouts. This has contributed to keeping the market for third-party upgrades very small. Only a few companies have produced SSDs in Apple-specific form factors, most notably Other World Computing (OWC) and Transcend. Transcend has generally used Silicon Motion controllers while OWC has used SandForce controllers, but until now their offerings have been limited to SATA-based SSDs.

Apple migrated their notebook SSDs to PCIe-based interfaces in 2013 and has been using drives supplied by Toshiba, SanDisk, and Samsung. OWC has finally devised a compatible replacement and released it as part of their Aura SSD product line. Like the Apple originals, the OWC Aura PCIe SSD uses the AHCI protocol; Apple so far only supports and uses NVMe on the Retina MacBook that doesn't have a removable SSD. The requirement to use AHCI instead of NVMe limited OWC's choices for SSD controller. While Apple is a big enough customer to convince Samsung to make the SM951 in a custom form factor, OWC is not. Marvell has shipped several AHCI-compatible PCIe SSD controllers, but their typical business model is to sell just the controller 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.

In order to keep costs under control, OWC has opted to not use a native PCIe SSD controller. Instead, the PCIe Aura SSD uses a Marvell 9230 SATA RAID controller and a pair of Silicon Motion SM2256 SATA SSD controllers. The Marvell 9230 has a 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. The PCIe Aura SSD's RAID design unfortunately does not support passing through TRIM commands nor retrieving SMART information from the individual SSD controllers.

Based on 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. That leaves the PCIe Aura SSD with capacity as its only strong selling point. The MacBook Air can be configured with up to 512GB of storage from Apple, but the Aura SSD can provide up to 960GB. Many Apple customers are put off by the steep price of build-to-order SSD upgrades: $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. At $347.99 for 480GB and $597.99 for 960GB, OWC's Aura manages to be both much cheaper than Apple's SSD upgrades and much more expensive than single-controller drives with a standard form factor.

The Aura SSD is sold either 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. The drive is expected to start shipping in late March.