Power Management

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.

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.

We report two idle power measurements. Active idle is representative of a typical desktop, where none of the advanced PCIe link or NVMe power saving features are enabled and the drive is immediately ready to process new commands. The idle power consumption metric is measured with PCIe Active State Power Management L1.2 state enabled and NVMe APST enabled.

Active Idle Power Consumption (No LPM)Idle Power Consumption

Idle power usage seems to have taken a step backward from the Crucial MX300 to the Crucial MX500. Both the active idle and the slumber power state consumption are higher than most mainstream SATA SSDs, but it isn't one of the extreme outliers that has broken power management.

Idle Wake-Up Latency

The idle wake-up time for the Crucial MX500 of about 1ms is higher than many mainstream drives, but is a big improvement over the 3.3ms of the Crucial MX300. The Marvell-based drives from Western Digital/SanDisk seem to offer the best combination of low power consumption and quick wake-ups.

Mixed Read/Write Performance Conclusion
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  • Kristian Vättö - Tuesday, December 19, 2017 - link

    The BX300 is merely a vehicle to consume low yielding MLC wafers. Reply
  • oRAirwolf - Tuesday, December 19, 2017 - link

    Can you expand on that statement? Low yielding in what ways? Reply
  • hojnikb - Tuesday, December 19, 2017 - link

    Probably not as good performing (endurance, write performance) dies get used with bx300 instead of discarding them or using them elsewhere. Reply
  • jabber - Tuesday, December 19, 2017 - link

    But where else would Crucial be using the good MLC ones if everything else is TLC? Reply
  • cblakely - Tuesday, December 19, 2017 - link

    Enterprise products Reply
  • Kristian Vättö - Wednesday, December 20, 2017 - link

    Most of it is going to mobile and industrial applications, of which both have very strict quality requirements. The ones that don't meet the criteria can either be sold as wafer/component or used in a retail client SSD, the latter obviously having a better profit margin.

    Memory is yielded at wafer level. Dies from a low yielding wafer statistically have a higher probability of failure in long-term, even if individual dies are OK in initial probing.
    Reply
  • sonny73n - Wednesday, December 20, 2017 - link

    WTH are you talking about? Testing endurance and write performance of every die? It's not common sense at all. Therefore, you're a bullshit. Reply
  • FunBunny2 - Wednesday, December 20, 2017 - link

    "WTH are you talking about? Testing endurance and write performance of every die? It's not common sense at all. Therefore, you're a bullshit. "

    that's not what he said. what he said was, post mortem analyses have shown that wafers with a low yield produce dies with short lifespans. those dies are then shipped out as retail SSD.
    Reply
  • emvonline - Tuesday, December 19, 2017 - link

    Kristian is a wise man. BX300 is a pragmatic response ... not a strategy. MX500 is very well positioned Reply
  • malventano - Tuesday, December 19, 2017 - link

    Low yield MLC wafers would likely not produce usable TLC dies with a higher endurance rating than Samsung's currently shipping V-NAND. Reply

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