The Toshiba RC100 SSD Review: Tiny Drive In A Big Market
by Billy Tallis on June 14, 2018 9:00 AM ESTPower 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.
| Toshiba RC100 NVMe Power and Thermal Management Features |
|||
| Controller | Toshiba unknown | ||
| Firmware | ADRA0101 | ||
| NVMe Version |
Feature | Status | |
| 1.0 | Number of operational (active) power states | 3 | |
| 1.1 | Number of non-operational (idle) power states | 2 | |
| Autonomous Power State Transition (APST) | Supported | ||
| 1.2 | Warning Temperature | 82 °C | |
| Critical Temperature | 85 °C | ||
| 1.3 | Host Controlled Thermal Management | Supported | |
| Non-Operational Power State Permissive Mode | Not Supported | ||
The Toshiba RC100 supports a fairly complete set of power and thermal management features. The RC100 is well-equipped to be kept within the often tight power and thermal limits of the small form factor machines it was originally designed for as a BGA SSD. The three active power states cover a reasonably wide range of power limits. Based on the transition latency ratings, there's no reason for a system to bother with the shallower PS3 idle state if the deeper PS4 state can be used.
| Toshiba RC100 NVMe Power States |
|||||
| Controller | Toshiba unknown | ||||
| Firmware | ADRA0101 | ||||
| Power State |
Maximum Power |
Active/Idle | Entry Latency |
Exit Latency |
|
| PS 0 | 3.3 W | Active | - | - | |
| PS 1 | 2.7 W | Active | - | - | |
| PS 2 | 2.3 W | Active | - | - | |
| PS 3 | 50 mW | Idle | 10 ms | 45 ms | |
| PS 4 | 5 mW | Idle | 10 ms | 50 ms | |
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.
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 if supported.
The active idle power consumption of the RC100 is about 1W, which is fairly typical for NVMe SSDs but a bit surprising for this drive in particular given its low-power focus. As with many drives, the deepest NVMe power state doesn't work out of the box with our desktop testbed, leaving it with substantially worse idle power draw than typical SATA drives and some NVMe drives.
The idle wake-up latency of the RC100 is in the 3-4ms range which is plenty fast and far better than the drive's pessimistic 45-50ms specification.
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Mikewind Dale - Thursday, June 14, 2018 - link
Interesting review. Thanks.I'm hoping that smaller, 11" and 13" laptops will start offering M.2 2242 instead of eMMC. I've been wary of purchasing a smaller laptop because I'm afraid that if the NAND ever reaches its lifespan, the laptop will be dead, with no way to replace the storage. An M.2 2242 would solve that problem.
PeachNCream - Thursday, June 14, 2018 - link
Boot options in the BIOS may allow you to select USB or SD as an option in the event that a modern eMMC system suffers from a soldered on drive failure. In that case, it's still possible to boot from an OS and use the computer. In that case, I'd go for some sort of lightweight Linux OS for performance reasons, but even a full distro works okay on USB 3.0 and up. SD is a slower option, but you may not want your OS drive to protrude from the side of the computer. Admittedly, that's a sort of cumbersome solution to keeping a low-budget PC alive when replacement costs aren't usually that high.peevee - Thursday, June 14, 2018 - link
"but this is only on platforms with properly working PCIe power management, which doesn't include most desktops"Billy, could you please elaborate on this?
artifex - Thursday, June 14, 2018 - link
Yeah, I'd also like to hear more about this.Billy Tallis - Thursday, June 14, 2018 - link
I've never encountered a desktop motherboard that had PCIe ASPM on by default, so at most it's a feature for power users and OEMs that actually care about power management. I've seen numerous motherboards that didn't even have the option of enabling PCIe ASPM, but the trend from more recent products seems to be toward exposing the necessary controls. Among boards that do let you fully enable ASPM, it's still possible for using it to expose bugs with peripherals that breaks things—sometimes the peripheral in question is a SSD. The only way I'm able to get low-power idle measurements out of PCIe SSDs on the current testbed is to tell Linux to ignore what the motherboard firmware says and force PCIe ASPM on, but this doesn't work for everything. Without some pretty sensitive power measurement equipment, it's almost impossible for an ordinary desktop user to know if their PCIe SSD is actually achieving the <10mW idle power that most drives advertise.peevee - Thursday, June 14, 2018 - link
So by "properly working" you mean "on by default in BIOS"? Or there are actual implementation bugs in some Intel or AMD CPUs or chipsets?Billy Tallis - Thursday, June 14, 2018 - link
Implementation bugs seem to be primarily a problem with peripheral devices (including peripherals integrated on the motherboard), which is why motherboard manufacturers are often justified in having ASPM off by default or entirely unavailable.AdditionalPylons - Thursday, June 14, 2018 - link
That's very interesting. And thanks Billy for a nice review! I too appreciate you doing something different. There will unfortunately always be someone angry on the Internet.Kwarkon - Friday, June 15, 2018 - link
L1.2 is a special PCIe link state that requires hardware CLREQ signal. When L1.2 is active all communication on PCIe is down thus both host and NVME device do not have to listen for data.Desktops don't have this signal ( it is grounded), so even if you tell the SSD (NVME admin commands) that L1.2 support is enabled it will still not be able to negotiate it.
In most cases m.2 NVME require certain PCIe link state to get lowest power for their Power State.
The PS x are just states that if all conditions are met than the SSD will get its power down to somewhere around stated value.
You can always check tech specs of the NVME. If in fact low power is supported than the lowest power will be stated as "deep sleep L1.2 " or similar.
Death666Angel - Saturday, June 16, 2018 - link
Prices in Germany do not line up one bit with the last chart. :D The HP EX920 1TB is 335€ and the ADATA SX8200 960GB is 290€. The SBX just has a weird amazon.de reseller who sells the 512GB version for 200€. The 970 Evo 1TB is 330€ and the Intel 760p 1TB is 352€. And for completeness, the WD Black 1TB is 365€. Even when accounting for exchange rates and VAT, the relative prices are nowhere near the US ones. :)