Power Management Features

Real-world client storage workloads leave SSDs idle most of the time, so the active power measurements presented earlier in this review only account for a small part of what determines a drive's suitability for battery-powered use. Especially under light use, the power efficiency of a SSD is determined mostly be how well it can save power when idle.

For many NVMe SSDs, the closely related matter of thermal management can also be important. M.2 SSDs can concentrate a lot of power in a very small space. They may also be used in locations with high ambient temperatures and poor cooling, such as tucked under a GPU on a desktop motherboard, or in a poorly-ventilated notebook.

The Sabrent Rocket Q claims support for the full range of NVMe power and thermal management features. However, the table of power states includes frighteningly high maximum power draw numbers for the active power states—over 17 W is really pushing it for a M.2 drive. Fortunately, we never measured consumption getting that high. The idle power states look typical, including the promise of quick transitions in and out of idle.

Note that the above tables reflect only the information provided by the drive to the OS. The power and latency numbers are often very conservative estimates, but they are what the OS uses to determine which idle states to use and how long to wait before dropping to a deeper idle state.

Idle Power Measurement

SATA SSDs are tested with SATA link power management disabled to measure their active idle power draw, and with it enabled for the deeper idle power consumption score and the idle wake-up latency test. Our testbed, like any ordinary desktop system, cannot trigger the deepest DevSleep idle state.

Idle power management for NVMe SSDs is far more complicated than for SATA SSDs. NVMe SSDs can support several different idle power states, and through the Autonomous Power State Transition (APST) feature the operating system can set a drive's policy for when to drop down to a lower power state. There is typically a tradeoff in that lower-power states take longer to enter and wake up from, so the choice about what power states to use may differ for desktop and notebooks, and depending on which NVMe driver is in use. Additionally, there are multiple degrees of PCIe link power savings possible through Active State Power Management (APSM).

We report three idle power measurements. Active idle is representative of a typical desktop, where none of the advanced PCIe link power saving features are enabled and the drive is immediately ready to process new commands. Our Desktop Idle number represents what can usually be expected from a desktop system that is configured to enable SATA link power management, PCIe ASPM and NVMe APST, but where the lowest PCIe L1.2 link power states are not available. The Laptop Idle number represents the maximum power savings possible with all the NVMe and PCIe power management features in use—usually the default for a battery-powered system but not always achievable on a desktop even after changing BIOS and OS settings. Since we don't have a way to enable SATA DevSleep on any of our testbeds, SATA drives are omitted from the Laptop Idle charts.

Note: Last year we upgraded our power measurement equipment and switched to measuring idle power on our Coffee Lake desktop, our first SSD testbed to have fully-functional PCIe power management. The below measurements are not a perfect match for the older measurements in our reviews from before that switch.

The Samsung 870 QVO SSDs have lower active idle power consumption than the NVMe competition, though our measurements of the 4TB model did catch it while it was still doing some background work. With SATA link power management enabled the 8TB 870 QVO draws more power than the smaller models, but is still very reasonable.

The Sabrent Rocket Q's idle power numbers are all decent but not surprising. The desktop idle power draw is significantly higher than the 49mW the drive claims for power state 3, but it's still only at 87mW which is not a problem.

The Samsung 870 QVO takes 1ms to wake up from sleep. The Sabrent Rocket Q has almost no measurable wake-up latency from the intermediate desktop idle state, but takes a remarkably long 108ms to wake up from the deepest sleep state. This is one of the slowest wake-up times we've measured from a NVMe drive and considerably worse than the 25ms latency the drive itself promises to the OS.

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