'\" t
.\"     Title: nvme-wdc-smart-log-add
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\"      Date: 06/28/2017
.\"    Manual: NVMe Manual
.\"    Source: NVMe
.\"  Language: English
.\"
.TH "NVME\-WDC\-SMART\-LO" "1" "06/28/2017" "NVMe" "NVMe Manual"
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.SH "NAME"
nvme-wdc-smart-log-add \- Send NVMe WDC smart\-log\-add Vendor Unique Command, return result
.SH "SYNOPSIS"
.sp
.nf
\fInvme wdc smart\-log\-add\fR <device> [\-\-interval=<NUM>, \-i <NUM>] [\-\-output\-format=<normal|json> \-o <normal|json>]
.fi
.SH "DESCRIPTION"
.sp
For the NVMe device given, send a Vendor Unique WDC smart\-log\-add command and provide the additional smart log\&. The \-\-interval option will return performance statistics from the specified reporting interval\&.
.sp
The <device> parameter is mandatory and may be either the NVMe character device (ex: /dev/nvme0)\&.
.sp
This will only work on WDC devices supporting this feature\&. Results for any other device are undefined\&.
.sp
On success it returns 0, error code otherwise\&.
.SH "OPTIONS"
.PP
\-i <NUM>, \-\-interval=<NUM>
.RS 4
Return the statistics from specific interval, defaults to 14
.RE
.PP
\-o <format>, \-\-output\-format=<format>
.RS 4
Set the reporting format to
\fIhuman\fR, or
\fIjson\fR\&. Only one output format can be used at a time\&. Default is human\&.
.RE
.sp
Valid Interval values and description :\-
.TS
allbox tab(:);
ltB ltB.
T{
Value
T}:T{
Description
T}
.T&
lt lt
lt lt
lt lt
lt lt
lt lt.
T{
.sp
\fB1\fR
T}:T{
.sp
Most recent five (5) minute accumulated set\&.
T}
T{
.sp
\fB2\-12\fR
T}:T{
.sp
Previous five (5) minute accumulated sets\&.
T}
T{
.sp
\fB13\fR
T}:T{
.sp
The accumulated total of sets 1 through 12 that contain the previous hour of accumulated statistics\&.
T}
T{
.sp
\fB14\fR
T}:T{
.sp
The statistical set accumulated since power\-up\&.
T}
T{
.sp
\fB15\fR
T}:T{
.sp
The statistical set accumulated during the entire lifetime of the device\&.
T}
.TE
.sp 1
.SH "OUTPUT EXPLANATION"
.TS
allbox tab(:);
ltB ltB.
T{
Field
T}:T{
Description
T}
.T&
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt.
T{
.sp
\fBHost Read Commands\fR
T}:T{
.sp
Number of host read commands received during the reporting period\&.
T}
T{
.sp
\fBHost Read Blocks\fR
T}:T{
.sp
Number of 512\-byte blocks requested during the reporting period\&.
T}
T{
.sp
\fBAverage Read Size\fR
T}:T{
.sp
Average Read size is calculated using (Host Read Blocks/Host Read Commands)\&.
T}
T{
.sp
\fBHost Read Cache Hit Commands\fR
T}:T{
.sp
Number of host read commands that serviced entirely from the on\-board read cache during the reporting period\&. No access to the NAND flash memory was required\&. This count is only updated if the entire command was serviced from the cache memory\&.
T}
T{
.sp
\fBHost Read Cache Hit Percentage\fR
T}:T{
.sp
Percentage of host read commands satisfied from the cache\&.
T}
T{
.sp
\fBHost Read Cache Hit Blocks\fR
T}:T{
.sp
Number of 512\-byte blocks of data that have been returned for Host Read Cache Hit Commands during the reporting period\&. This count is only updated with the blocks returned for host read commands that were serviced entirely from cache memory\&.
T}
T{
.sp
\fBAverage Read Cache Hit Size\fR
T}:T{
.sp
Average size of read commands satisfied from the cache\&.
T}
T{
.sp
\fBHost Read Commands Stalled\fR
T}:T{
.sp
Number of host read commands that were stalled due to a lack of resources within the SSD during the reporting period (NAND flash command queue full, low cache page count, cache page contention, etc\&.)\&. Commands are not considered stalled if the only reason for the delay was waiting for the data to be physically read from the NAND flash\&. It is normal to expect this count to equal zero on heavily utilized systems\&.
T}
T{
.sp
\fBHost Read Commands Stalled Percentage\fR
T}:T{
.sp
Percentage of read commands that were stalled\&. If the figure is consistently high, then consideration should be given to spreading the data across multiple SSDs\&.
T}
T{
.sp
\fBHost Write Commands\fR
T}:T{
.sp
Number of host write commands received during the reporting period\&.
T}
T{
.sp
\fBHost Write Blocks\fR
T}:T{
.sp
Number of 512\-byte blocks written during the reporting period\&.
T}
T{
.sp
\fBAverage Write Size\fR
T}:T{
.sp
Average Write size calculated using (Host Write Blocks/Host Write Commands)\&.
T}
T{
.sp
\fBHost Write Odd Start Commands\fR
T}:T{
.sp
Number of host write commands that started on a non\-aligned boundary during the reporting period\&. The size of the boundary alignment is normally 4K; therefore this returns the number of commands that started on a non\-4K aligned boundary\&. The SSD requires slightly more time to process non\-aligned write commands than it does to process aligned write commands\&.
T}
T{
.sp
\fBHost Write Odd Start Commands Percentage\fR
T}:T{
.sp
Percentage of host write commands that started on a non\-aligned boundary\&. If this figure is equal to or near 100%, and the NAND Read Before Write value is also high, then the user should investigate the possibility of offsetting the file system\&. For Microsoft Windows systems, the user can use Diskpart\&. For Unix\-based operating systems, there is normally a method whereby file system partitions can be placed where required\&.
T}
T{
.sp
\fBHost Write Odd End Commands\fR
T}:T{
.sp
Number of host write commands that ended on a non\-aligned boundary during the reporting period\&. The size of the boundary alignment is normally 4K; therefore this returns the number of commands that ended on a non\-4K aligned boundary\&.
T}
T{
.sp
\fBHost Write Odd End Commands Percentage\fR
T}:T{
.sp
Percentage of host write commands that ended on a non\-aligned boundary\&.
T}
T{
.sp
\fBHost Write Commands Stalled\fR
T}:T{
.sp
Number of host write commands that were stalled due to a lack of resources within the SSD during the reporting period\&. The most likely cause is that the write data was being received faster than it could be saved to the NAND flash memory\&. If there was a large volume of read commands being processed simultaneously, then other causes might include the NAND flash command queue being full, low cache page count, or cache page contention, etc\&. It is normal to expect this count to be non\-zero on heavily utilized systems\&.
T}
T{
.sp
\fBHost Write Commands Stalled Percentage\fR
T}:T{
.sp
Percentage of write commands that were stalled\&. If the figure is consistently high, then consideration should be given to spreading the data across multiple SSDs\&.
T}
T{
.sp
\fBNAND Read Commands\fR
T}:T{
.sp
Number of read commands issued to the NAND devices during the reporting period\&. This figure will normally be much higher than the host read commands figure, as the data needed to satisfy a single host read command may be spread across several NAND flash devices\&.
T}
T{
.sp
\fBNAND Read Blocks\fR
T}:T{
.sp
Number of 512\-byte blocks requested from NAND flash devices during the reporting period\&. This figure would normally be about the same as the host read blocks figure
T}
T{
.sp
\fBAverage NAND Read Size\fR
T}:T{
.sp
Average size of NAND read commands\&.
T}
T{
.sp
\fBNAND Write Commands\fR
T}:T{
.sp
Number of write commands issued to the NAND devices during the reporting period\&. There is no real correlation between the number of host write commands issued and the number of NAND Write Commands\&.
T}
T{
.sp
\fBNAND Write Blocks\fR
T}:T{
.sp
Number of 512\-byte blocks written to the NAND flash devices during the reporting period\&. This figure would normally be about the same as the host write blocks figure\&.
T}
T{
.sp
\fBAverage NAND Write Size\fR
T}:T{
.sp
Average size of NAND write commands\&. This figure should never be greater than 128K, as this is the maximum size write that is ever issued to a NAND device\&.
T}
T{
.sp
\fBNAND Read Before Write\fR
T}:T{
.sp
This is the number of read before write operations that were required to process non\-aligned host write commands during the reporting period\&. See Host Write Odd Start Commands and Host Write Odd End Commands\&. NAND Read Before Write operations have a detrimental effect on the overall performance of the device\&.
T}
.TE
.sp 1
.SH "EXAMPLES"
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Has the program issue WDC smart\-log\-add Vendor Unique Command with default interval (14) :
.sp
.if n \{\
.RS 4
.\}
.nf
# nvme wdc smart\-log\-add /dev/nvme0
.fi
.if n \{\
.RE
.\}
.RE
.SH "NVME"
.sp
Part of the nvme\-user suite\&.