Provided by: sysstat_12.0.1-1build1_amd64 bug

NAME

       tapestat - Report tape statistics.

SYNOPSIS

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

DESCRIPTION

       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

       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

       --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

       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

       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).

              Note:  On  Debian  sysstems  the  colors  are  displayed  by default when output is
              connected to the terminal, even if this variable is not set (i.e. unset variable is
              treated as if it were set to auto).

              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

       /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).

FILES

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

       /proc/uptime contains system uptime.

AUTHOR

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

SEE ALSO

       iostat(1), mpstat(1)

       https://github.com/sysstat/sysstat

       http://pagesperso-orange.fr/sebastien.godard/