It seems the full text is not available online, just the start this is the URL: The article I refer to appeared in the 1/2017 issue of c’t, a German IT paper. You don’t need to use vendor-specific tools (like isdct). For this example, the Write Amplification Factor (WAF) is 16185227 / 6405605 = 2.53Īs you can see, the NVMe command line tools provide a lot of good information for understanding the health and performance of NVMe devices. This ratio is measured in writes to NAND and writes to HOST. The scale of these values is not very important, as they are the most helpful for finding the write amplification of your workload. The bytes written to the NVMe storage from the system. For this device, the measured unit seems to be in 32MB values. This shows if the device is throttled due to overheating, and when there were throttling events in the past. The percentage of IO operations that were reads (since the workload timer was reset). The media wear by the current “workload.” This device allows you to measure some statistics from the time you reset them (called the “workload”) in addition to showing the device lifetime values. In this case, it looks like the cells are rated for 1800 writes and about 1100 on average were used This shows how much of the rated cell life was used, as well as the min/max/avg write count for different cells. The time in minutes a device operated above a warning or critical temperature. Warning Temperature Time/Critical Temperature Time. Depending on the NVMe device you’re using, an unsafe shutdown might corrupt user data. The number of times a power loss happened without a shutdown notification being sent. This can be used to gauge long-term storage load trends. Time in minutes that the controller was busy servicing commands. Using this value, as well as one below, you can compute the average IO size for “physical” reads and writes.Ĭontroller Busy Time. The number of commands of the appropriate type issued. So you can multiply this value by 512000 to get value in bytes. The first value corresponds to 1000 of the 512-byte units. This is the number of 512-byte data units that are read/written, but it is measured in an unusual way. (Note: the number can be more than 100% if you’re using storage for longer than its planned life.)ĭata Units Read/Data Units Written. Contains a vendor specific estimate of the percentage of the NVM subsystem life used, based on actual usage and the manufacturer’s prediction of NVM life. (Note: I’m not quite sure what the practical meaning of “asynchronous event completion” is, but it looks like something to avoid!) The value is indicated as a normalized percentage (0 to 100%). When the Available Spare capacity falls below the threshold indicated in this field, an asynchronous event completion can occur. Contains a normalized percentage (0 to 100%) of the remaining spare capacity that is available.Īvailable Spare Threshold. After looking at the NVMe specification document, here is my read on some of the data:Īvailable Spare. Some of this information is self-explanatory, and some of it isn’t. Vendor Specific SMART Attributes with Thresholds: SMART Attributes Data Structure revision number: 16 Smartctl 6.5 r4214 (local build)Ĭopyright (C) 2002-16, Bruce Allen, Christian Franke, = START OF READ SMART DATA SECTION =
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