Linux IO Performance Monitoring parameters explained

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The above columns have the following meanings:

RRQM/S: The number of times per second read requests to the device are merged, and the file system merges requests to read the same block

wrqm/s: Number of times per second write requests to the device are merged

R/S: Number of reads completed per second

W/S: Number of writes completed per second

RKB/S: Amount of Read data per second (KB)

WKB/S: Amount of Write data per second (in kilobytes)

Avgrq-sz: The average amount of data per IO operation (units of sectors)

Avgqu-sz: Average queue Length of IO requests waiting to be processed

Await: Average per IO request wait time (including wait time and processing time, in milliseconds)

SVCTM: Average processing time per IO request (in milliseconds)

%util: The time ratio used for IO operations in cycles, that is, the time ratio of IO queue non-empty

Command: iostat-d-x-m (M) 10 (SEC)

device:         rrqm/s   wrqm/s      r/s     w/s    rmb/s    wmb/s  avgrq-sz avgqu-sz   await  svctm  %utilsda                0.00     2.10     0.00   42.50     0.00      9.14   440.56     1.60   37.65    0.39   1.66dm-0               0.00     0.00    0.00   44.60      0.00     9.14   419.82      1.63   36.46   0.36   1.62dm-1               0.00     0.00    0.00     0.00     0.00     0.00      0.00     0.00    0.00   0.00   0.00

For the example output above, we can obtain the following information:

Write about 30M data (wkb/s value) to disk per second

91 IO operations per second (R/S+W/S), with write as the principal

Average per IO request waits 120.57 milliseconds, processing time is 6.33 milliseconds

In the queue of IO requests waiting to be processed, there are an average of 11.79 requests residing

There is also a connection between the above values, and we can calculate other values by some value, for example:

Util = (r/s+w/s) * (svctm/1000)

For the above examples are: Util = (1+90) * (6.33/1000) = 0.57603

Linux IO Performance Monitoring parameters explained