Drive power state

Depend on motherboard support the way PCIe ASPM does, so it should eventually reach the same widespread availability that SATA Link Power Management enjoys.We report two idle power values for each drive: an active idle measurement taken with none of the above power management states engaged, and an idle power measurement with either SATA LPM Slumber state or the lowest-power NVMe non-operational power state, if supported.Western Digital has done something unusual with idle power management on the WD Black. On most NVMe SSDs, idle power consumption is quite bad unless the operating system specifically requests that the drive enter a low power state, or if the OS gives the drive permission to use the NVMe autonomous power state transition (APST) feature. The WD Black seems to use an equivalent to APST even if that feature is not turned on by the OS. The reason why APST usually requires OS intervention to enable is that it gives the OS the opportunity to inform the SSD of how much latency is acceptable when waking up from a low power state, and how long the drive should sit idle before dropping down to a lower power state that will take longer to wake up from. (Recall that NVMe SSDs can define many power states, where SATA drives are effectively limited to just two, or three on platforms that support DevSleep.)When a drive chooses to use autonomous power savings even if the OS doesn't ask for it, the drive should ensure that it does

Status LEDs and Buttons This section contains information for interpreting front, rear, and internal LED states. Front-Panel LEDs Figure 1. Front Panel LEDs Table 1. Front Panel LEDs, Definition of States LED Name States 1 SAS SAS/SATA drive fault Note NVMe solid state drive (SSD) drive tray LEDs have different behavior than SAS/SATA drive trays. Off—The hard drive is operating properly. Amber—Drive fault detected. Amber, blinking—The device is rebuilding. Amber, blinking with one-second interval—Drive locate function activated in the software. 2 SAS SAS/SATA drive activity LED Off—There is no hard drive in the hard drive tray (no access, no fault). Green—The hard drive is ready. Green, blinking—The hard drive is reading or writing data. 1 NVMe NVMe SSD drive fault Note NVMe solid state drive (SSD) drive tray LEDs have different behavior than SAS/SATA drive trays. Off—The drive is not in use and can be safely removed. Green—The drive is in use and functioning properly. Green, blinking—the driver is initializing following insertion or the driver is unloading following an eject command. Amber—The drive has failed. Amber, blinking—A drive Locate command has been issued in the software. 2 NVMe NVMe SSD activity Off—No drive activity. Green, blinking—There is drive activity. 3 Power button/LED Off—There is no AC power to the server. Amber—The server is in standby power mode. Power is supplied only to the Cisco IMC and some motherboard functions. Green—The server is in main power mode. Power is supplied to all server components. 4 Unit identification Off—The unit identification function is not in use. Blue, blinking—The unit identification function is activated. 5 System health Green—The server is running in normal operating condition. Green, blinking—The server is performing system initialization and memory check. Amber, steady—The server is in a degraded operational state (minor fault). For example: Power supply redundancy is lost.

Mechanism, analogous to the SATA Link Power Management mechanism. Both define two power saving modes: an intermediate power saving mode with strict wake-up latency requirements (eg. 10µs for SATA "Partial" state) and a deeper state with looser wake-up requirements (eg. 10ms for SATA "Slumber" state). SATA Link Power Management is supported by almost all SSDs and host systems, though it is commonly off by default for desktops. PCIe ASPM support on the other hand is a minefield and it is common to encounter devices that do not implement it or implement it incorrectly. Forcing PCIe ASPM on for a system that defaults to disabling it may lead to the system locking up; this is the case for our current SSD testbed and thus we are unable to measure the effect of PCIe ASPM on SSD idle power.The NVMe standard also defines a drive power management mechanism that is separate from PCIe link power management. The SSD can define up to 32 different power states and inform the host of the time taken to enter and exit these states. Some of these power states can be operational states where the drive continues to perform I/O with a restricted power budget, while others are non-operational idle states. The host system can either directly set these power states, or it can declare rules for which power states the drive may autonomously transition to after being idle for different lengths of time. NVMe power management including Autonomous Power State Transition (APST) fortunately does not