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NAME | SYNOPSIS | DESCRIPTION | REPORT | OPTIONS | CONSIDERATIONS | ENVIRONMENT | BUGS | FILES | AUTHOR | SEE ALSO | COLOPHON |
TAPESTAT(1) Linux User's Manual TAPESTAT(1)
tapestat - Report tape statistics.
tapestat [ -k | -m ] [ -t ] [ -V ] [ -y ] [ -z ] [ --human ] [
interval [ count ] ]
The tapestat command is used for monitoring the activity of tape
drives connected to a system.
The first report generated by the tapestat command provides
statistics concerning the time since the system was booted, unless
the -y option is used, when this first report is omitted. Each
subsequent report covers the time since the previous report.
The interval parameter specifies the amount of time in seconds
between each report. The count parameter can be specified in
conjunction with the interval parameter. If the count parameter is
specified, the value of count determines the number of reports
generated at interval seconds apart. If the interval parameter is
specified without the count parameter, the tapestat command generates
reports continuously.
The tapestat report provides statistics for each tape drive connected
to the system. The following data are displayed:
r/s
The number of reads issued expressed as the number per second
averaged over the interval.
w/s
The number of writes issued expressed as the number per second
averaged over the interval.
kB_read/s | MB_read/s
The amount of data read expressed in kilobytes (by default or
if option -k used) or megabytes (if option -m used) per second
averaged over the interval.
kB_wrtn/s | MB_wrtn/s
The amount of data written expressed in kilobytes (by default
or if option -k used) or megabytes (if option -m used) per
second averaged over the interval.
%Rd
Read percentage wait - The percentage of time over the
interval spent waiting for read requests to complete. The
time is measured from when the request is dispatched to the
SCSI mid-layer until it signals that it completed.
%Wr
Write percentage wait - The percentage of time over the
interval spent waiting for write requests to complete. The
time is measured from when the request is dispatched to the
SCSI mid-layer until it signals that it completed.
%Oa
Overall percentage wait - The percentage of time over the
interval spent waiting for any I/O request to complete (read,
write, and other).
Rs/s
The number of I/Os, expressed as the number per second
averaged over the interval, where a non-zero residual value
was encountered.
Ot/s
The number of I/Os, expressed as the number per second
averaged over the interval, that were included as "other".
Other I/O includes ioctl calls made to the tape driver and
implicit operations performed by the tape driver such as
rewind on close (for tape devices that implement rewind on
close). It does not include any I/O performed using methods
outside of the tape driver (e.g. via sg ioctls).
--human
Print sizes in human readable format (e.g. 1k, 1.23M, etc.)
The units displayed with this option supersede any other
default units (e.g. kilobytes, sectors...) associated with
the metrics.
-k Show the amount of data written or read in kilobytes per
second instead of megabytes. This option is mutually
exclusive with -m.
-m Show the amount of data written or read in megabytes per
second instead of kilobytes. This option is mutually
exclusive with -k.
-t Display time stamps. The time stamp format may depend on the
value of the S_TIME_FORMAT environment variable (see below).
-V Print version and exit.
-y Omit the initial statistic showing values since boot.
-z Tell tapestat to omit output for any tapes for which there was
no activity during the sample period.
It is possible for a percentage value (read, write, or other) to be
greater than 100 percent (the tapestat command will never show a
percentage value more than 999). If rewinding a tape takes 40
seconds where the interval time is 5 seconds the %Oa value would show
as 0 in the intervals before the rewind completed and then show as
approximately 800 percent when the rewind completes.
Similar values will be observed for %Rd and %Wr if a tape drive stops
reading or writing and then restarts (that is it stopped streaming).
In such a case you may see the r/s or w/s drop to zero and the
%Rd/%Wr value could be higher than 100 when reading or writing
continues (depending on how long it takes to restart writing or
reading). This is only an issue if it happens a lot as it may cause
tape wear and will impact on the backup times.
For fast tape drives you may see low percentage wait times. This
does not indicate an issue with the tape drive. For a slower tape
drive (e.g. an older generation DDS drive) the speed of the tape (and
tape drive) is much slower than filesystem I/O, percent wait times
are likely to be higher. For faster tape drives (e.g. LTO) the
percentage wait times are likely to be lower as program writing to or
reading from tape is going to be doing a lot more filesystem I/O
because of the higher throughput.
Although tape statistics are implemented in the kernel using atomic
variables they cannot be read atomically as a group. All of the
statistics values are read from different files under /sys, because
of this there may be I/O completions while reading the different
files for the one tape drive. This may result in a set of statistics
for a device that contain some values before an I/O completed and
some after.
This command uses rounding down as the rounding method when
calculating per second statistics. If, for example, you are using dd
to copy one tape to another and running tapestat with an interval of
5 seconds and over the interval there were 3210 writes and 3209 reads
then w/s would show 642 and r/s 641 (641.8 rounded down to 641). In
such a case if it was a tar archive being copied (with a 10k block
size) you would also see a difference between the kB_read/s and
kB_wrtn/s of 2 (one I/O 10k in size divided by the interval period of
5 seconds). If instead there were 3210 writes and 3211 reads both w/s
and r/s would both show 642 but you would still see a difference
between the kB_read/s and kB_wrtn/s values of 2 kB/s.
This command is provided with an interval in seconds. However
internally the interval is tracked per device and can potentially
have an effect on the per second statistics reported. The time each
set of statistics is captured is kept with those statistics. The
difference between the current and previous time is converted to
milliseconds for use in calculations. We can look at how this can
impact the statistics reported if we use an example of a tar archive
being copied between two tape drives using dd. If both devices
reported 28900 kilobytes transferred and the reading tape drive had
an interval of 5001 milliseconds and the writing tape drive 5000
milliseconds that would calculate out as 5778 kB_read/s and 5780
kB_wrtn/s.
The impact of some retrieving statistics during an I/O completion,
rounding down, and small differences in the interval period on the
statistics calculated should be minimal but may be non-zero.
The tapestat command takes into account the following environment
variables:
S_COLORS
When this variable is set, display statistics in color on the
terminal. Possible values for this variable are never, always
or auto (the latter is the default).
Please note that the color (being red, yellow, or some other
color) used to display a value is not indicative of any kind
of issue simply because of the color. It only indicates
different ranges of values.
S_COLORS_SGR
Specify the colors and other attributes used to display
statistics on the terminal. Its value is a colon-separated
list of capabilities that defaults to
H=31;1:I=32;22:M=35;1:N=34;1:Z=34;22. Supported capabilities
are:
H= SGR (Select Graphic Rendition) substring for percentage
values greater than or equal to 75%.
I= SGR substring for tape names.
M= SGR substring for percentage values in the range from
50% to 75%.
N= SGR substring for non-zero statistics values.
Z= SGR substring for zero values.
S_TIME_FORMAT
If this variable exists and its value is ISO then the current
locale will be ignored when printing the date in the report
header. The tapestat command will use the ISO 8601 format
(YYYY-MM-DD) instead. The timestamp displayed with option -t
will also be compliant with ISO 8601 format.
/sys filesystem must be mounted for tapestat to work. It will not
work on kernels that do not have sysfs support
This command requires kernel version 4.2 or later (or tape statistics
support backported for an earlier kernel version).
/sys/class/scsi_tape/st<num>/stats/* Statistics files for tape
devices.
/proc/uptime contains system uptime.
Initial revision by Shane M. SEYMOUR (shane.seymour <at> hpe.com)
Modified for sysstat by Sebastien Godard (sysstat <at> orange.fr)
iostat(1), mpstat(1)
http://pagesperso-orange.fr/sebastien.godard/
This page is part of the sysstat (sysstat performance monitoring
tools) project. Information about the project can be found at
⟨http://sebastien.godard.pagesperso-orange.fr/⟩. If you have a bug
report for this manual page, send it to systat-AT-orange.fr. This
page was obtained from the project's upstream Git repository
⟨https://github.com/sysstat/sysstat.git⟩ on 2017-07-05. If you dis‐
cover any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
Linux MAY 2017 TAPESTAT(1)
Pages that refer to this page: cifsiostat(1), iostat(1)