tapestat(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | REPORT | OPTIONS | CONSIDERATIONS | ENVIRONMENT | BUGS | FILES | AUTHOR | SEE ALSO | COLOPHON

TAPESTAT(1)                Linux User's Manual               TAPESTAT(1)

NAME         top

       tapestat - Report tape statistics.

SYNOPSIS         top

       tapestat [ -k | -m ] [ -t ] [ -V ] [ -y ] [ -z ] [ --human ] [
       interval [ count ] ]

DESCRIPTION         top

       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.

REPORT         top

       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).

OPTIONS         top

       --human
              Print sizes in human readable format (e.g. 1.0k, 1.2M,
              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.

CONSIDERATIONS         top

       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.

ENVIRONMENT         top

       The tapestat command takes into account the following environment
       variables:

       S_COLORS
              By default statistics are displayed in color when the
              output is connected to a terminal.  Use this variable to
              change the settings. Possible values for this variable are
              never, always or auto (the latter is equivalent to the
              default settings).
              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.

BUGS         top

       /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).

       Although tapestat speaks of kilobytes (kB), megabytes (MB)..., it
       actually uses kibibytes (kiB), mebibytes (MiB)...  A kibibyte is
       equal to 1024 bytes, and a mebibyte is equal to 1024 kibibytes.

FILES         top

       /sys/class/scsi_tape/st<num>/stats/*
              Statistics files for tape devices.

       /proc/uptime contains system uptime.

AUTHOR         top

       Initial revision by Shane M. SEYMOUR (shane.seymour <at> hpe.com)
       Modified for sysstat by Sebastien Godard (sysstat <at> orange.fr)

SEE ALSO         top

       iostat(1), mpstat(1)

       https://github.com/sysstat/sysstat 
       http://pagesperso-orange.fr/sebastien.godard/ 

COLOPHON         top

       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 sysstat-AT-orange.fr.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/sysstat/sysstat.git⟩ on 2021-04-01.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-02-15.)  If you discover 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                           JUNE 2020                    TAPESTAT(1)

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