SanDisk Professional PRO-G40 Thunderbolt / USB High-Performance Rugged SSD

In a recent article on AnandTech, Ganesh gives us their review on the new SanDisk Professional PRO-G40 Thunderbolt / USB Dual-Mode Portable SSD Review. Western Digital's introduction of the SanDisk Professional PRO-G40 dual-mode PSSD is a promising solution for prosumers, content creators, and studios in need of a high-performance portable storage drive. The fact that it is rugged and bus-powered adds to its convenience and portability.

The PRO-G40 PSSD offers three storage capacities, 1T, 2TB,  and 4TB, providing options to suit different storage needs. Its maximum performance reaches close to 3GBps when connected to Thunderbolt 3 hosts, which is impressive for those who require fast data transfer speeds.

Moreover, the PRO-G40 PSSD ensures wide compatibility by functioning as a 1GBps-class drive when connected to a USB 3.2 Gen 2 host port. This means that even if a Thunderbolt 3 connection is not available, users can still achieve high-speed data transfers with USB 3.2 Gen 2.

The PRO-G40 PSSD from SanDisk Professional is a versatile and capable portable SSD that caters to the needs of professionals and content creators, offering both speed and durability.


The use of external bus-powered storage devices has indeed seen significant advancements in both storage capacity and speeds in recent years. This progress has been made possible by innovations in flash technology, such as 3D NAND and NVMe, as well as faster host interfaces like Thunderbolt 3 and USB 3.x. As a result, we now have compact flash-based storage devices that can deliver speeds of 3GBps and higher. While Thunderbolt 4 can achieve these speeds, USB remains the primary interface for mass-market devices.

In the past, the initial wave of Thunderbolt 3-based portable SSDs and enclosures faced limited market acceptance due to their incompatibility with traditional USB ports. However, Intel's Titan Ridge controllers introduced an intriguing feature when used in client devices like peripherals and docks. These controllers included not only downstream PCIe lanes but also a USB 3.2 Gen 2 host interface. This allowed manufacturers to develop unique dual-mode designs by modifying the traditional JHL7440 Thunderbolt 3 SSD. The USB 3.2 Gen 2 downstream port was connected to the upstream interface of a USB to NVMe bridge chip. Depending on the host to which the drive was connected, the PCIe 3.0 x4 lanes of the NVMe SSD were connected either to the JHL7440's downstream PCIe 3.0 x4 lanes or the bridge chip's PCIe 3.0 x4 lanes. The Sabrent ROCKET XTRM-Q was one of the early portable SSD lineups to support dual-mode operation based on this architecture.

Now, Western Digital is joining the dual-mode trend with the introduction of the SanDisk Professional PRO-G40 Portable SSD. This SSD utilizes the WD_BLACK SN750E M.2 2280 drive internally. The JHL7440 Titan Ridge Thunderbolt 3 controller is paired with the ASMedia ASM2362 USB 3.2 Gen 2 - NVMe bridge chip to enable dual-mode operation. The enclosure of the PRO-G40 is stylishly designed, featuring a solid aluminum construction with a silicone base covering one side. Additionally, the drive includes convenient features like an LED indicator and a metal-reinforced USB-C port.

Overall, the SanDisk Professional PRO-G40 Portable SSD from Western Digital combines performance, style, and dual-mode functionality, catering to users who require both high-speed Thunderbolt 3 performance and compatibility with traditional USB ports.

The PRO-G40 PSSD boasts an impressive IP68 rating, which means it offers complete protection against dust ingress and can withstand being submerged under 1 meter of water without suffering any damage. This level of ruggedness makes it suitable for use in challenging environments. Additionally, the solid aluminum core contributes to its durability by providing drop-resistance of up to 3 meters and crush-resistance of up to 4000 lbs. The aluminum construction also aids in heat dissipation, ensuring the drive remains cool during operation.

In terms of packaging, the PRO-G40 PSSD comes in a minimal package that includes the main unit and a short 20cm Thunderbolt 3 passive cable. It's worth noting that the cable length might be a concern for desktop setups that require longer cables to connect the drive. However, it is important to consider that these dual-mode drives are primarily designed for use with notebooks or systems that incorporate a Thunderbolt dock as part of the workspace. In such scenarios, the shorter cable length is typically sufficient.

Overall, the PRO-G40 PSSD's ruggedness, including its IP68 rating and drop/crush-resistance, combined with the inclusion of a short Thunderbolt 3 cable, make it a convenient and robust portable storage solution for on-the-go professionals and content creators.

The drive is formatted for Macs out of the box, but it is simple to reformat in one's preferred operating system. Their sample was tested on a Windows 10 machine using the exFAT filesystem. The 'issues' that have plagued all Thunderbolt SSDs on Windows also affect the SanDisk Professional PRO-G40. Unless write caching is enabled in the volume policies for the Thunderbolt port-connected drive, write performance falls short of expectations.

Since moving to Windows 10 on their new testbed, their policy has been to evaluate all external storage devices with default OS settings - and this has been for quick removal. They did, however, test the PRO-G40 drive three times: once with a Thunderbolt 3 port and once with a USB 3.2 Gen 2x2 port enabled by the ASMedia ASM2342 controller. They repeated the evaluation procedure with the write cache settings changed in their final pass.

CrystalDiskInfo provides a quick overview of the PSSD as seen by the host system. The interface section is of particular interest - NVM Express over Thunderbolt, and UASP (NVM Express) over USB 3.2 Gen 2x2 Type-C.

The table below presents a comparative view of the specifications of the different PSSDs presented in this review.

Read the full article from AnandTech HERE

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