Crucial Portable SSD X6 and X8 2TB Review: QLC for Storage On-the-Goby Ganesh T S on October 21, 2020 8:00 AM EST
Miscellaneous Aspects and Concluding Remarks
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 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 (SATA-Class)
Both the HP P600 and the ADATA SC680 show signs of a SLC cache. On the other hand, the X6 starts off at around 200 MBps and goes down to around 35 MBps after 240GB of continuous writes. At 195 MBps, the drive already starts off with low expectations, and there is not much to write home about.
|Sequential Write to 90% of Disk Capacity - Performance Consistency (NVMe-Class)
The X8, on the other hand, performs admirably with the SLC cache - For around 256GB of continuous writes, the drive provides 825 MBps+ of bandwidth before slipping down to around 150 MBps for the direct-to-QLC writes. The reason for the X8's stellar performance for normal workloads lies in this SLC cache. Normal workloads rarely go beyond this huge cache, and that is enough to make the X8 lead the charts in almost all tests. The problem is when the SLC cache runs out - as is possible for creative professionals transferring huge work files. Crucial does mention read-intensive workloads as the main focus of the drive, and hence folks with those types of workloads may well prefer SSDs such as the SanDisk Extreme PRO v2.
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 3.0 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 (SATA-Class)
The X6 seems to have a power consumption profile similar to other drives in the set. The 1W+ idling number is a bit too high for our liking when attempting to use the drive with battery-powered devices, but the competition is not much better in any case.
|Drive Power Consumption - CrystalDiskMark Workloads (NVMe-Class)
The X8 2TB version consumes less power than the 1TB version from last year. In addition, the peak power consumption is the lowest for the X8 2TB drive. Idle power consumption is not as good, with the OWC Envoy PRO EX USB-C being much more efficient on that front.
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.
|SATA-Class External Flash Storage Devices - Pricing
|Street Price (USD)
|Price per GB (USD/GB)
|ADATA SC680 960GB
|Crucial Portable SSD X6 2TB
|HP P600 500GB
The X6 is not very competitively priced, particularly given the pricing for the higher-performance 2TB drives belonging to the NVMe class. In fact, just an additional $15 gets the consumer to the WD My Passport 2TB NVMe external SSD.
|NVMe-Class External Flash Storage Devices - Pricing
|Street Price (USD)
|Price per GB (USD/GB)
|Crucial Portable SSD X8 1TB
|WD My Passport SSD (2020) 1TB
|Crucial Portable SSD X8 2TB
|SanDisk Extreme Portable SSD v2 1TB
|SanDisk Extreme PRO Portable SSD v2 2TB
|OWC Envoy Pro EX USB-C 2TB
The X8 also falls into the same category - the pricing is simply too high for a QLC drive. At $307, it is even priced higher than the 2TB My Passport NVMe SSD. Though we haven't reviewed the 2TB version of the My Passport SSD (2020), our experience with the 1TB version was quite satisfactory.
After careful analysis of various aspects (including benchmark numbers, temperatures, power consumption, and pricing), it is clear that the Crucial Portable SSD X8 is an excellent choice for normal consumer workloads. The X6, unfortunately, is not as attractive given its pricing. In the X8, Crucial must be appreciated for delivering a SSD for those types of workloads that successfully manages to hide the shortcomings of QLC. Unfortunately, users have to shell out for the highest-capacity version to get the 256GB of SLC cache (The 1TB version has half the cache). The thermal profile of both drives is good enough to prevent them from getting too hot to touch. The X8 gets our recommendation for normal consumer workloads, but the Western Digital drives are a better choice for creative professionals and users with write-intensive workloads, and they currently cost less than the X8. The absence of any IP rating and hardware encryption are minor quibbles, but Crucial does offer drop-protection with both the X6 and the X8. In the end, the recommendation for the end-user will depend on the expected usage scenarios.