====== blktrace ======
---- dataentry analysisTool ----
name           : blktrace
features_ttags : monitoring
layers_ttags   : operating system, block device
version        : 2.0.0 (2007-09-10)
license_ttag   : GPL
----
blktrace is used to analyze I/O-access, it provides more a more detailed look at I/O-usage than other tools like iotop and iostat.
===== Usage =====
Analyzing I/O patterns with blktrace is done in two steps. First use ''blktrace'' to log operations, then use ''blkparse'' to show a detailed report on the recorded data.

Record I/O-events on the blockdevice ''/dev/sda'' for five seconds:
<code>
blktrace -w 5 -d /dev/sda
</code>

Print contents of the logfile to stdout (use -s switch to show per-program statistics at the end):
<code>
blkparse -i sda.blktrace.0 -s
</code>

Another option is to pass data into ''blkparse'' straigt away to enable live viewing:
<code>
blktrace -d /dev/sda -o - | blkparse -i -
</code>
===== Output =====
After recording the data blktrace shows a small summary of the recorded events:
<code>
=== sda ===
  CPU  0:                    3 events,        1 KiB data
  CPU  1:                  145 events,        7 KiB data
  CPU  2:                    6 events,        1 KiB data
  CPU  3:                    3 events,        1 KiB data
  CPU  4:                  295 events,       14 KiB data
  CPU  5:                    0 events,        0 KiB data
  CPU  6:                    0 events,        0 KiB data
  CPU  7:                   10 events,        1 KiB data
  Total:                   462 events (dropped 0),       22 KiB data
</code>
Since blkparse shows a huge amount of information we chose to only show small excerpts below.

Each event gets a single line in the first section of the log.
By default the following elements are shown in order:
|major and minor| major,minor device numbers (as shown in lsblk)|
|cpu|cpu-core|
|sequence| sequencenumber is|
|pid| unix process id|
|action| one of is described in detail in the documentation| 
|rwbs|'r' for read, 'w' for write, 'd' for discard (for more details see the documentation)|
|starting block + number of blocks|Block the operation is starting at and the number of blocks affected respectively|


<code>
  8,0    1        2     0.000001084  5069  Q   W 240054272 + 2048 [dd]
  8,0    1        8     0.000058101  5069  Q   W 240056320 + 2048 [dd]
  8,0    1       13     0.000110909  5069  Q   W 240058368 + 2048 [dd]
  8,0    1       14     0.000113330  5069  G   W 240058368 + 2048 [dd]
  8,0    1       16     0.000162283  5069  Q   W 240060416 + 2048 [dd]
  8,0    1       17     0.000164598  5069  G   W 240060416 + 2048 [dd]
  8,0    1       28     0.000243672  5069  I   W 240058368 + 2048 [dd]
  8,0    1       29     0.000243966  5069  I   W 240060416 + 2048 [dd]
  8,0    1       36     0.000255103  5069  D   W 240058368 + 2048 [dd]
  8,0    1       37     0.000259523  5069  D   W 240060416 + 2048 [dd]
</code>

When the ''-s'' flag is set additional, per-process statistics are also displayed.
<code>
dd (5069)
 Reads Queued:           0,        0KiB  Writes Queued:           8,    5,696KiB
 Read Dispatches:        0,        0KiB  Write Dispatches:        8,    4,884KiB
 Reads Requeued:         0               Writes Requeued:         0
 Reads Completed:        0,        0KiB  Writes Completed:        0,        0KiB
 Read Merges:            0,        0KiB  Write Merges:            0,        0KiB
 IO unplugs:             1               Timer unplugs:           0
 Allocation wait:        0               Allocation wait:         0
 Dispatch wait:          0               Dispatch wait:           0
 Completion wait:        0               Completion wait:         0
</code>

A summary is shown at the very end of blkparse's output.
<code>
Total (sda):
 Reads Queued:           0,        0KiB  Writes Queued:          41,   10,904KiB
 Read Dispatches:        0,        0KiB  Write Dispatches:       20,   10,092KiB
 Reads Requeued:         0               Writes Requeued:         0
 Reads Completed:        0,        0KiB  Writes Completed:       21,   10,092KiB
 Read Merges:            0,        0KiB  Write Merges:           21,       84KiB
 IO unplugs:            12               Timer unplugs:           0

Throughput (R/W): 0KiB/s / 3,285KiB/s
Events (sda): 352 entries
Skips: 0 forward (0 -   0.0%)
</code>


===== Similar tools =====

---- datarelated ----
cols  : features, layers
max   : 5
sort  : ^name
----