Sabrent Rocket XTRM-Q USB / Thunderbolt 3 Dual Mode External SSD Review: Yin and Yang

The external storage market has shown renewed vigor in recent years, thanks in part to growth fueled by bus-powered flash-based storage solutions. The introduction of 3D NAND, coupled with the increasing confidence of manufacturers in QLC (4-bits per cell) has brought down the cost of these drives to the point where even a reasonably spacious external SSD can be had for an equally reasonable price. And though this means that NAND manufacturers like Western Digital, Samsung, and Crucial/Micron have an inherent advantage in terms of vertical integration, the availability of cheap flash in the open market has also enabled other vendors to come up with innovative solutions.

Today, we’re looking at a unique product in the external SSD market – the Sabrent Rocket XTRM-Q. A true dual-mode Thunderbolt 3/USB drive, the Rocket XTRM-Q can be natively used with both Thunderbolt 3 and USB hosts. This means that it can deliver speeds over 2GBps on a Thunderbolt 3 connection, or fall back to USB mode and still deliver 1GBps or more with a USB 3.2 Gen 2 connection. Compared to most external SSDs on the market, which are virtually always USB-only or Thunderbolt-only, this allows Sabrent’s drive to offer USB-style universal compatibility while still making the most of the host it’s connected to, using USB when it’s available, or upgrading to Thunderbolt as appropriate to let the drive run as fast as it can.

Meanwhile, not unlike their efforts with internal (M.2) products, Sabrent is also at the leading-edge of storage capacity with the Rocket XTRM-Q, offering versions of the drive with up to 8TB of storage. Overall, the Rocket XTRM-Q is available in capacities ranging from 500GB up to 8TB, with Sabrent using QLC NAND across the family to hit their price and capacity goals.

For this review we’re looking at two of the mid-tier Rocket XTRM-Q models – the 2TB and 4TB models – in order to size up the performance of the drives and see how they stack up against the other products in the market.

External bus-powered storage devices have grown both in storage capacity as well as speeds over the last decade. Thanks to rapid advancements in flash technology (including the advent of 3D NAND and NVMe) as well as faster host interfaces (such as Thunderbolt 3 and USB 3.2 Gen 2×2), we now have palm-sized flash-based storage devices capable of delivering 2GBps+ speeds. Depending on the performance profile and the components used, these flash drives fall into one of six categories:

  • 2.5GBps+ class: Thunderbolt SSDs with PCIe 3.0 x4 NVMe drives
  • 2GBps+ class: USB 3.2 Gen 2×2 SSDs with PCIe 3.0 x4 NVMe drives
  • 1GBps+ class: USB 3.2 Gen 2 SSDs with PCIe 3.0 (x4 or x2) NVMe drives
  • 500MBps+ class: USB 3.2 Gen 2 SSDs with SATA drives
  • 400MBps+ class: USB 3.2 Gen 1 SSDs with SATA drives
  • Sub-400MBps+ class: USB 3.2 Gen 1 flash drives with direct flash-to-USB controllers

Almost all external SSDs currently in the market can slot into one of the above categories. However, the Sabrent XTRM-Q we are looking at today is unique in falling into two categories in the above list. It is both a Thunderbolt 3 SSD and a USB 3.2 Gen 2 SSD.

 

The XTRM-Q uses the Intel JHL7440 (Titan Ridge) Thunderbolt 3 controller to interface with the host system. Similar to the JHL6xxx Alpine Ridge host controllers, Titan Ridge also has a built-in xHCI controller that enables it to act as a USB 3.2 Gen 2 host. When used in a device configuration (i.e, in docks or peripherals), Titan Ridge has an extra feature not available in Alpine Ridge – a USB 3.2 Gen 2 downstream interface. Sabrent has taken advantage of this with a nifty tweak in the standard Thunderbolt 3 SSD reference design. The USB 3.2 Gen 2 downstream port is connected to the upstream interface of a USB to NVMe bridge chip (a Realtek 9210PD in all likelihood, though Tom’s Hardware reports it as Realtek 9108B). Depending on the host to which the drive is connected (reported by the JHL7440), the PCIe 3.0 x4 lanes of the NVMe SSD are connected to either the JHL7440’s downstream PCIe 3.0 x4 lanes or the Realtek bridge chip’s PCIe 3.0 x4 lanes.

The Sabrent Rocket XTRM-Q’s compatibility with both Thunderbolt 3 and USB ports while providing different performance profiles made for an interesting evaluation exercise. The SSD also happens to be the first we have evaluated with Intel’s Titan Ridge controller. Based on these aspects, we evaluated the XTRM-Q models as well as a host of other SSDs with the following host controllers:

  • Thunderbolt 3 : Intel Alpine Ridge (JHL6540)
  • Thunderbolt 3 : Intel Titan Ridge (JHL 7540)
  • USB 3.2 Gen 2 : ASMedia ASM2142

Additional details are available further down in the sub-section dealing with our testbed setup and evaluation methodology.

The various graphs in this piece compare and contrast the performance of different external SSDs when used with different host ports. The complete list is provided below, with the host specified in brackets. Some entries do not have a host entry – the numbers presented for those are from its evaluation with our standard testbed using the Alpine Ridge (JHL6540) host.

  • Sabrent Rocket XTRM-Q 4TB [JHL6540]
  • Sabrent Rocket XTRM-Q 4TB [ASM2142]
  • Crucial Portable SSD X8 2TB
  • DIY TB3 SSD [TEKQ Rapide – WD Black SN750] [JHL6540]
  • DIY TB3 SSD [TEKQ Rapide – WD Black SN750] [JHL7540]
  • OWC Envoy Pro EX TB3 2TB [JHL6540]
  • OWC Envoy Pro EX USB-C 2TB
  • Plugable TBT3-NVME2TB 2TB [JHL6540]
  • Sabrent Rocket Nano Rugged 2TB
  • Sabrent Rocket XTRM-Q 2TB [ASM2142]
  • Sabrent Rocket XTRM-Q 2TB [JHL6540]
  • Sabrent Rocket XTRM-Q 2TB [JHL7540]
  • Sabrent Rocket XTRM-Q 4TB [JHL7540]
  • SanDisk Extreme PRO Portable SSD v2 2TB [ASM3242]
  • SanDisk Extreme PRO Portable SSD v2 2TB [JHL6540]

A quick overview of the internal capabilities of the storage devices is given by CrystalDiskInfo.

Drive Information

The Sabrent Rocket XTRM-Q uses standard PCIe 3.0 x4 NVMe drives internally. The bridge chip configuration allows for S.M.A.R.T passthrough and the SSDs support TRIM to maintain  optimal performance. The internal SSD is actually the Sabrent Rocket Q that was reviewed earlier this month.

Testbed Setup and Testing Methodology

Evaluation of DAS units on Windows is done with a Hades Canyon NUC configured as outlined below. We use one of the rear USB Type-C ports enabled by the Alpine Ridge controller for both Thunderbolt 3 and USB devices. However, to force the usage of the USB 3.2 Gen 2 interface in the Rocket XTRM-Q, the SSD was connected to the front USB Type-C port enabled by the ASMedia ASM2142 controller.

AnandTech DAS Testbed Configuration (JHL6540 and ASM2142 Hosts)
Motherboard Intel NUC8i7HVB
CPU Intel Core i7-8809G
Kaby Lake, 4C/8T, 3.1GHz (up to 4.2GHz), 14nm+, 8MB L2
Memory Crucial Technology Ballistix DDR4-2400 SODIMM
2 x 16GB @ 16-16-16-39
OS Drive Intel Optane SSD 800p SSDPEK1W120GA
(118 GB; M.2 Type 2280 PCIe 3.0 x2 NVMe; Optane)
SATA Devices Intel SSD 545s SSDSCKKW512G8
(512 GB; M.2 Type 2280 SATA III; Intel 64L 3D TLC)
Chassis Hades Canyon NUC
PSU Lite-On 230W External Power Brick
OS Windows 10 Enterprise x64 (v1909)
Thanks to Intel for the build components

We also evaluated the performance of some of the Thunderbolt 3 SSDs with a Titan Ridge host – the Ghost Canyon NUC. These SSDs carry a JHL7540 tag in their graph entries. The configuration of the Ghost Canyon NUC used for benchmarking purposes is specified below.

AnandTech DAS Testbed Configuration (JHL7540 Host)
Motherboard Intel NUC9i9QNB
CPU Intel Core i9-9980HK
Coffee Lake-H, 8C/16T, 2.4 (5.0) GHz, 14nm (optimized), 16MB L2+L3, 45W TDP
Memory Corsair Vengeance DDR4-2666 SODIMM
2 x 16GB @ 18-19-19-39
OS Drive Intel SSD 905p Optane SSDPEL1D380GA
(380 GB; M.2 Type 22110 PCIe 3.0 x4 NVMe; Optane / 3D XPoint)
Secondary Drive Kingston KC2000 SKC2000M81000G
(1TB; M.2 Type 2280 PCIe 3.0 x4 NVMe; Toshiba 96L 3D TLC; Silicon Motion SM2262EN Controller)
Chassis Ghost Canyon NUC
PSU FSP 500W 80 PLUS Platinum Internal Power Supply
OS Windows 10 Enterprise x64 (v1909)
Thanks to Intel, Kingston, and Corsair for the build components

Our evaluation methodology for direct-attached storage devices adopts a judicious mix of synthetic and real-world workloads. While most DAS units targeting a particular market segment advertise similar performance numbers and also meet them for common workloads, the real differentiation is brought out on the technical side by the performance consistency metric and the effectiveness of the thermal solution. Industrial design and value-added features may also be important for certain users. The remaining sections in this review tackle all of these aspects after analyzing the features of the drives in detail.

Sabrent packs its drives into metal cases, delivering the look and feel of a premium product. Inside the box, we have the main SSD and a box containing the cables – a USB 3.2 Gen 2 Type-C to Type-A one, and a Thunderbolt 3 Type-C to Type-C one. A note with directions to change the caching policy for the drive is also included, as shown in the picture below.

The write-caching policy problem is an issue for all Thunderbolt 3 SSDs in the market, and is not restricted to the Sabrent Rocket XTRM-Q. Despite the provided directions, we evaluate all SSDs (including our DIY Thunderbolt 3 SSD using the TEKQ Rapide enclosure and the WD Black SN750) in the default state with write caching turned off – This ensures we are comparing apples to apples even when the units under consideration use different host interfaces.

The Sabrent Rocket XTRM-Q is bundled with the longest Thunderbolt 3 cable (70cm) we have seen so far in any Thunderbolt 3 SSD. Sabrent also provides optional shockproof protection in the form of bumpers for the XTRM-Q. At less than 130g, the drives are light but the aluminum enclosure lends solidity.

The table below compares the features and characteristics of the various SSDs dealt with in the review today.

Direct-Attached Storage Characteristics
Aspect
Upstream Port USB 3.2 Gen 2 and Thunderbolt 3 Type-C USB 3.2 Gen 2 Type-C
Bridge / Controller Intel JHL7440 + Phison E12S-based Sabrent Rocket Q ASMedia ASM2362 + Silicon Motion SM2263
Flash Micron 96L 3D QLC Micron 96L 3D QLC
Power Bus Powered Bus Powered
     
Physical Dimensions 190 mm x 132 mm x 17.53 mm 110 mm x 53 mm x 11.5 mm
IP Rating N/A N/A
Weight 129 grams (without cable) 101 grams (without cable)
Cable ~50cm USB 3.2 Gen 2 Type-C to Type-A
~70cm Thunderbolt 3 (Type-C to Type-C)
23 cm USB 3.2 Gen 1 Type-C to Type-C
Type-C to Type-A adaptor bundled
     
S.M.A.R.T Passthrough Yes Yes
UASP Support Yes Yes
TRIM Passthrough Yes Yes
Encryption Support N/A N/A

The Sabrent Rocket XTRM-Q is available in capacities ranging from 500GB (with a MSRP of $230) to 8TB (with a MSRP of $2000). This high capacity is achieves thanks to the use of Micron’s 96L QLC NAND. QLC brings along a host of challenges related to endurance and slow write speeds. SSD vendors solve this by bringing in overprovisioning and SLC caching. Sabrent indicated that the XTRM-Q models come with around 9% over-provisioning out of the box. SLC cache size varies based on the drive capacity, and that is one of the aspects we evaluate further down in this review.

Sabrent claims speeds in excess of 2500MBps for the Rocket XTRM-Q. This is backed up by the ATTO benchmarks provided below on the read side, but the absence of write caching results in sub-1GBps performance for writes using the Thunderbolt 3 host ports. There is no discernible difference in the performance numbers when using either the JHL6540 or JHL7540 host. However, in the USB mode, the drives come close to 1GBps for both reads and writes (using the ASMedia ASM2142 host). These observations are common to both the 2TB and 4TB variants of the Rocket XTRM-Q. It must be noted that these access traces are not very common in real-life scenarios.

Drive Performance Benchmarks – ATTO

CrystalDiskMark, despite being a canned benchmark, provides a better estimate of the performance range with a selected set of numbers.

Drive Performance Benchmarks – CrystalDiskMark

In CrystalDiskMark, we see the 4TB version actually perform a bit worse compared to the 2TB version in the sequential reads with the Thunderbolt 3 host ports. However, in USB mode, both versions perform very similar to each other. In the USB mode, we can compare the 2TB version against the Crucial X8 for an apples-to-apples comparison – the numbers are in favor of the XTRM-Q across multiple traces.

In the next section, we take a look at real-world workloads along with an evaluation of the performance consistency.

Our testing methodology for DAS units takes into consideration the usual use-case for such devices. The most common usage scenario is transfer of large amounts of photos and videos to and from the unit. Other usage scenarios include the use of the DAS as a download or install location for games and importing files directly off the DAS into a multimedia editing program such as Adobe Photoshop. Some users may even opt to boot an OS off an external storage device.

The AnandTech DAS Suite tackles the first use-case. The evaluation involves processing three different workloads:

  • Photos: 15.6 GB collection of 4320 photos (RAW as well as JPEGs) in 61 sub-folders
  • Videos: 16.1 GB collection of 244 videos (MP4 as well as MOVs) in 6 sub-folders
  • BR: 10.7 GB Blu-ray folder structure of the IDT Benchmark Blu-ray

Each workload’s data set is first placed in a 25GB RAM drive, and a robocopy command is issued to transfer it to the DAS under test (formatted in NTFS). Upon completion of the transfer (write test), the contents from the DAS are read back into the RAM drive (read test). This process is repeated three times for each workload. Read and write speeds, as well as the time taken to complete each pass are recorded. Bandwidth for each data set is computed as the average of all three passes.

Blu-ray Folder Read

Despite the presentation of all the results for a given workload in one graph, the numbers above require careful analysis – we are essentially looking at three different sets:

  1. Thunderbolt 3 SSDs with JHL7540 host
  2. Thunderbolt 3 SSDs with JHL6540 host
  3. USB 3.2 Gen 2 SSDs

Only the first two sets are perfectly apples-to-apples – in fact, that is the case only when we consider the 2TB drives. The 4TB variant stands alone, as we have not evaluated any other 4TB Thunderbolt 3 SSD earlier. On the USB side, out evaluations so far have used the JHL6540’s USB host capabilities – but the XTRM-Q variants could only be evaluated in this mode using the ASMedia ASM2142.

Going back to the results, we see our DIY SSD coming out on top across most workloads with the JHL7540 host. A notable exception is for the video reads, where the 2TB XTRM-Q wins out. However, it must be kept in mind that we are comparing 1TB, 2TB, and 4TB drives in this set. Moving on to the JHL6540 host, we again see the write workloads turning out to be the weak point for the XTRM-Q drives. The 2TB Plugable and OWC drives are apples-to-apples and they consistently out-perform (or match, at worst) the XTRM-Q. The usage of QLC NAND is likely to be the culprit in this case. In the USB mode, the XTRM-Q drives acquit themselves well. There is no significant gulf in the numbers between the different USB 3.2 Gen 2 SSDs in this mode. For all practical purposes, the casual user will notice no difference between them in the course of normal usage.

Performance Consistency

Beyond basic file copying benchmarks, power users may also want to dig deeper to understand the limits of each device. To address this concern, we also instrumented our evaluation scheme for determining performance consistency. Aspects influencing the performance consistency include SLC caching and thermal throttling / firmware caps on access rates to avoid overheating. This is important for power users, as the last thing that they want to see when copying over 100s of GB of data is the transfer rate going down to USB 2.0 speeds.

In addition to tracking the instantaneous read and write speeds of the DAS when processing the AnandTech DAS Suite, the temperature of the drive was also recorded at the beginning and end of the processing. In earlier reviews, we used to track the temperature all through. However, we have observed that SMART read-outs for the temperature in NVMe SSDs using USB 3.2 Gen 2 bridge chips end up negatively affecting the actual transfer rates. To avoid this problem, we have restricted ourselves to recording the temperature at either end of the actual workloads set. The graphs below present the recorded data.

Performance Consistency and Thermal Characteristics

The first three sets of writes and reads correspond to the photos suite. A small gap (for the transfer of the video suite from the internal SSD to the RAM drive) is followed by three sets for the video suite. Another small RAM-drive transfer gap is followed by three sets for the Blu-ray folder. An important point to note here is that each of the first three blue and green areas correspond to 15.6 GB of writes and reads respectively. The low write speeds with Thunderbolt 3 hosts are evident in the graphs, but they are remarkably consistent across different sets of workloads pointing to the SLC cache not running out for this traffic pattern. The thermal design is also excellent – the internal SSD temperaturee goes slightly north of 50C in only one of the six graphs of interest above.

There are a number of storage benchmarks that can subject a device to artificial access traces by varying the mix of reads and writes, the access block sizes, and the queue depth / number of outstanding data requests. We saw results from two popular ones – ATTO, and CrystalDiskMark – in a previous section. More serious benchmarks, however, actually replicate access traces from real-world workloads to determine the suitability of a particular device for a particular workload. Real-world access traces may be used for simulating the behavior of computing activities that are limited by storage performance. Examples include booting an operating system or loading a particular game from the disk.

PCMark 10’s storage bench (introduced in v2.1.2153) includes four storage benchmarks that use relevant real-world traces from popular applications and common tasks to fully test the performance of the latest modern drives:

  • The Full System Drive Benchmark uses a wide-ranging set of real-world traces from popular applications and common tasks to fully test the performance of the fastest modern drives. It involves a total of 204 GB of write traffic.
  • The Quick System Drive Benchmark is a shorter test with a smaller set of less demanding real-world traces. It subjects the device to 23 GB of writes.
  •  
  • The Data Drive Benchmark is designed to test drives that are used for storing files rather than applications. These typically include NAS drives, USB sticks, memory cards, and other external storage devices. The device is subjected to 15 GB of writes.
  • The Drive Performance Consistency Test is a long-running and extremely demanding test with a heavy, continuous load for expert users. In-depth reporting shows how the performance of the drive varies under different conditions. This writes more than 23 TB of data to the drive.

Despite the data drive benchmark appearing most suitable for testing direct-attached storage, we opted to run the full system drive benchmark as part of our evaluation flow. Many of us use portable flash drives as boot drives and storage for Steam games. These types of use-cases are addressed only in the full system drive benchmark.

The Full System Drive Benchmark comprises of 23 different traces. For the purpose of presenting results, we classify them under five different categories:

  • Boot: Replay of storage access trace recorded while booting Windows 10
  • Creative: Replay of storage access traces recorded during the start up and usage of Adobe applications such as Acrobat, After Effects, Illustrator, Premiere Pro, Lightroom, and Photoshop.
  • Office: Replay of storage access traces recorded during the usage of Microsoft Office applications such as Excel and Powerpoint.
  • Gaming: Replay of storage access traces recorded during the start up of games such as Battlefield V, Call of Duty Black Ops 4, and Overwatch.
  • File Transfers: Replay of storage access traces (Write-Only, Read-Write, and Read-Only) recorded during the transfer of data such as ISOs and photographs.

PCMark 10 also generates an overall score, bandwidth, and average latency number for quick comparison of different drives. The sub-sections in the rest of the page reference the access traces specified in the PCMark 10 Technical Guide.

Booting Windows 10

The read-write bandwidth recorded for each drive in the boo access trace is presented below.

Windows 10 Boot

In the Thunderbolt 3 mode, the XTRM-Q models (despite their excellent read speeds evident in the synthetic access traces) makes up the rear end of the pack. However, in USB mode, they perform much better. The 2TB version delivers the best result when compared against all the othe USB 3.2 Gen 2 SSDs.

Creative Workloads

The read-write bandwidth recorded for each drive in the sacr, saft, sill, spre, slig, sps, aft, exc, ill, ind, psh, and psl access traces are presented below.

Startup - Adobe Acrobat

The performance of the XTRM-Q drives for creative workloads in the Thunderbolt 3 mode is nothing to write home about. However, in USB mode the drives perform well, with the 2TB version again performing a bit better than the 4TB one in most workloads.

Office Workloads

The read-write bandwidth recorded for each drive in the exc and pow access traces are presented below.

Usage - Microsoft Excel

The disappointment in the Thunderbolt 3 performance is compensated by the passable numbers in the USB mode for office workloads.

Gaming Workloads

The read-write bandwidth recorded for each drive in the bf, cod, and ow access traces are presented below.

Startup - Battlefield V

Most gaming workloads are read-intensive, and this works well for the XTRM-Q models. Across all three test configurations (JHL7540 host, JHL6540 host, and USB mode), the 2TB version performs admirably, while the 4TB version performs well enough to be in the middle of the pack.

Files Transfer Workloads

The read-write bandwidth recorded for each drive in the cp1, cp2, cp3, cps1, cps2, and cps3 access traces are presented below.

Duplicating ISOs (Read-Write)

The numbers here are similar to our DAS suite (robocopy) workload. It is the same story, with the USB mode performing well, while the Thunderbolt 3 mode is onlly passable.

Overall Scores

PCMark 10 reports an overall score based on the observed bandwidth and access times for the full workload set. The score, bandwidth, and average access latency for each of the drives are presented below.

Full System Drive Benchmark Bandwidth (MBps)

The overall scores reflect our inferences from the previous set of tests – the 2TB performs better than the 4TB version for the most part, and the USB mode delivers competitive performance (again, for the 2TB version in particular). When compared against other Thunderbolt 3 SSDs, the performance numbers are strictly average.

The performance of the drives in various real-world access traces as well as synthetic workloads was brought out in the preceding sections. We also looked at the performance consistency for these cases. Power users may also be interested in performance consistency under worst-case conditions, as well as drive power consumption. The latter is also important when the drives are used with battery powered devices such as notebooks and smartphones. Pricing is also an important aspect. We analyze each of these in detail below.

Worst-Case Performance Consistency

Flash-based storage devices tend to slow down in unpredictable ways when subject to a large number of small-sized random writes. Many benchmarks use that scheme to pre-condition devices prior to the actual testing in order to get a worst-case representative number. Fortunately, such workloads are uncommon for direct-attached storage devices, where workloads are largely sequential in nature. Use of SLC caching as well as firmware caps to prevent overheating may cause drop in write speeds when a flash-based DAS device is subject to sustained sequential writes.

Our Sequential Writes Performance Consistency Test configures the device as a raw physical disk (after deleting configured volumes). A fio workload is set up to write sequential data to the raw drive with a block size of 128K and iodepth of 32 to cover 90% of the drive capacity. The internal temperature is recorded at either end of the workload, while the instantaneous write data rate and cumulative total write data amount are recorded at 1-second intervals.

Sequential Write to 90% of Disk Capacity – Performance Consistency

The first analysis is for the Thunderbolt 3 SSDs – no major differences were noted in the behavior when connected to the JHL6540 and JHL7540 host ports. Our DIY configuration peaks at 2400MBps+ till its SLC cache runs out, before dropping down to the 600MBps range for the rest of the workload. This actually represents the best of the lot. The Phison-based designs from Plugable and OWC perform similarly, with three distinct performance levels – 550 MBps, 150 MBps, and ~80MBps. All these drives use 3D TLC NAND, and the SLC caching behavior is quite predictable. The XTRM-Q drives, on the other hand, start off badly with 175MBps as the first level for the 4TB version and 240MBps for the 2TB version. The second level is ~75MBps (with huge variation) for both drives.

In the USB mode, the performance is much better – in fact, we can decipher the SLC cache size in this configuration. The 4TB drive is able to maintain 950MBps+ for 1033 seconds (pointing to a SLC cache of around 968GB) before settling down to ~180MBps (with significant swings between ~40MBps and ~200MBps). The 2TB drive behaves much better, though the SLC cache size is halved. It maintains 950MBps+ for 517 seconds (around 485GB SLC cache size) before settling down to a much steadier 195MBps. The worst-case temperature in the six graphs of interest turned out to be only 64C, pointing again to the effectiveness of the thermal solution.

Power Consumption

Bus-powered devices can configure themselves to operate within the power delivery constraints of the host port. While Thunderbolt 3 ports are guaranteed to supply up to 15W for client devices, USB 2.0 ports are guaranteed to deliver only 4.5W (900mA @ 5V). In this context, it is interesting to have a fine-grained look at the power consumption profile of the various drives. Using the Plugable USBC-TKEY, the bus power consumption of the drives was tracked while processing the CrystalDiskMark workloads (separated by 30s intervals). The graphs below plot the instantaneous bus power consumption against time, while singling out the maximum and minimum power consumption numbers.

Drive Power Consumption – CrystalDiskMark Workloads

In the Thunderbolt 3 mode, the 4TB version operates between 2.08W and 6.02W with the JHL6540 and 2.01W and 9.23W with the JHL7540. The corresponding numbers for the 2TB drive are (2.07W, 6.76W) and (2.01W, 6.56W). In the USB mode, the 4TB drive operates between 1.11W and 5.19W, while the 2TB version operates between 1.10W and 5.19W. The power consumption in the USB mode is acceptable, though we have seen external SSDs from Samsung that enter lower power states quite frequently (enabling them to work well with battery-powered devices). In the Thunderbolt mode, the power consumption is lower than our DIY configuration, and approximately in the same ballpark as the other Thunderbolt 3 SSDs we are comparing them against.

Pricing

The price of flash-based storage devices tend to fluctuate quite a bit over time. However, the relative difference between different models usually doesn’t change. The table below summarizes the product links and pricing for the various units discussed in the review.

External Flash Storage Devices – Pricing
Product Model Number Capacity (GB) Street Price (USD) Price per GB (USD/GB)
Crucial Portable SSD X8 2TB CT2000X8SSD9 2000 $307 0.153
Sabrent Rocket Nano Rugged 2TB SB-2TB-NAWP 2000 $330 0.165
Sabrent Rocket XTRM-Q 2TB SB-XTMQ-2TB 2000 $350 0.175
Sabrent Rocket XTRM-Q 4TB SB-XTMQ-4TB 4000 $700 0.175
SanDisk Extreme PRO Portable SSD v2 2TB SDSSDE81-2T00 2000 $350 0.175
OWC Envoy Pro EX USB-C 2TB ENVPROC2N20 1920 $349 0.182
OWC Envoy Pro EX TB3 2TB OWCTB3ENVP20 2000 $480 0.24
DIY TB3 SSD [TEKQ Rapide – WD Black SN750] OWCTB3ENVP20 1000 $245 0.245
Plugable TBT3-NVME2TB 2TB TBT3-NVME2TB 2000 $499 0.249

The Sabrent Rocket XTRM-Q drives are the cheapest Thunderbolt 3 SSDs in the market by a huge margin – In fact, the Plugable TBT3-NVME2TB and the OWC Envoy Pro EX TB3 2TB drives cost at least $130 more than the 2TB XTRM-Q. This is the first drive we have seen with QLC delivering the promised low-priced high-capacity SSD from a consumer perspective. The 4TB version has the same cost per GB, but its high capacity makes it a premium product with a $700 price tag.

Final Words

The Sabrent Rocket XTRM-Q represents a unique product line in the market – a dual-mode SSD that can work with both Thunderbolt 3 ports and USB ports with optimal performance profiles based on the host to which the drive is connected. It is also available in capacities that no other external SSD vendor offers. These two aspects ensure that the XTRM-Q can appeal to a select audience in a way that no other offering can match. Pricing is also attractive on a $-per-GB basis, and the thermal solution is excellent.

The use of QLC NAND could be a turn-off for some folks, though Sabrent has sought to address that with a liberal amount of SLC cache – almost 25% of the drive capacity. Unfortunately, there seem to be other problems – or at least quirks – on the write caching front. For medium-sized sustained writes, there’s a sizable gap in performance between Thunderbolt 3 and USB modes, leaving the normally more capable Thunderbolt 3 mode at a disadvantage. This disappointing write performance in Thunderbolt 3 mode is quite puzzling – given that these slow write speeds don’t occur in USB mode, it hints that SLC write caching is not being under in Thunderbolt 3 mode. But even then, our DIY configuration with the same write caching functionality turned off is able to deliver much better numbers.

Overall, although the Rocket XTRM-Q is a dual-mode drive, it has a distinct yin and yang dichotomy going on, which depends on the host type. As a Thunderbolt 3 device the drive can put up some great read speeds, which is what you’d expect with an NVMe-based drive backed by Thunderbolt 3’s raw bandwidth. However write performance very clearly favors USB mode, as this is the only mode that seems to be able to take advantage of the drive’s speedy SLC cache. It’s strangely unbalanced performance that partially undermines what would otherwise should be the drive’s biggest strength: a USB drive that’s able to upgrade to Thunderbolt 3 for even better performance on compatible hosts.

Thunderbolt 3 performance aside, it’s also unfortunate that the internal SSD is pretty much inaccessible. The unit as a whole is sealed shut, which means that in case of an unlikely board or bridge chip failure, the ability to recover data by attaching the internal drive to another computer is pretty much ruled out. Other than the Crucial Portable X6 and X8, we haven’t seen any of the other external SSDs (with the flash and bridge chips on separate boards) keep their internal drive out of reach. Hopefully, this is an aspect that Sabrent can address in the future.

Otherwise, Sabrent would also do well to release a 3D TLC version of the dual-mode platform to address some of the shortcomings of the XTRM-Q while retaining the positives. This is likely still a generation off (we’ve yet to see the prerequisite 8TB TLC M.2 drives), but it would help boost the drive’s minimum write performance, which it never hurts to improve on.