Crucial Portable SSD X6 and X8 2TB Review: QLC for Storage On-the-Go

Synthetic Benchmarks - ATTO and CrystalDiskMark

SATA SSDs behind a USB 3.1 Gen 2 bridge claim speeds of around 550 MBps. Crucial claims 540 MBps, and the ATTO benchmarks for the X6 back up those claims. Unfortunately, these access traces are not very common in real-life scenarios.

SATA-Class External Drives Performance Benchmarks - ATTO

Crucial Portable SSD X6 2TBADATA SC680 960GBHP P600 500GBExpand All

The reads approach the SATA bandwidth limits, but the writes are held back by the DRAM-less nature of the SSD controller and the QLC flash - ATTO maxes out around 370 MBps for those types of transfers. The HP P600 fares much better, but the X6 is better than the ADATA SC680 (it must be kept in mind that we are comparing different capacity points).

CrystalDiskMark, despite being a canned benchmark, provides a better estimate of the performance range with a selected set of numbers. As evident from the screenshot below, the performance can dip to as low as 11MBps for low-queue depth random writes.

SATA-Class External Drives Performance Benchmarks - CrystalDiskMark

Crucial Portable SSD X6 2TBADATA SC680 960GBHP P600 500GBExpand All

Most USB 3.1 Gen 2 drives with NVMe SSDs claim speeds of around 1000 MBps, as does the Crucial Portable SSD X8.

NVMe-Class External Drives Performance Benchmarks - ATTO

Crucial Portable SSD X8 2TBCrucial Portable SSD X8 1TBOWC Envoy Pro EX USB-C 2TBSanDisk Extreme PRO Portable SSD v2 2TB [JHL6540]SanDisk Extreme Portable SSD v2 1TBWD My Passport SSD (2020) 1TBExpand All

Here, we see typical USB 3.1 Gen 2 external SSD speeds - upwards of 900 MBps for writes, and close to 1GBps for reads. CrystalDiskMark provides a better estimate of the performance range with a selected set of numbers. As evident from the screenshot below, the performance can dip to as low as 31MBps for low-queue depth random reads.

NVMe-Class External Drives Performance Benchmarks - CrystalDiskMark

Crucial Portable SSD X8 2TBCrucial Portable SSD X8 1TBOWC Envoy Pro EX USB-C 2TBSanDisk Extreme PRO Portable SSD v2 2TB [JHL6540]SanDisk Extreme Portable SSD v2 1TBWD My Passport SSD (2020) 1TBExpand All

We see slightly better overall performance in the 2TB version compared to the 1TB one for these workloads. Compared to the SanDisk Extreme PRO v2 connected to a USB 3.2 Gen 2 port (the other recent 2TB SSD we have reviewed), the X8 falls slightly behind on the sequential workloads, though random reads are better. Most DAS workloads are of the former type.