Última modificació: setembre de 2015
El paquet sysstat en proporciona tres eines de monitorització:
Anem a veure com podem utilitzar iostat. Si l'executem obtindrem alguna cosa semblant a això:
bmw@usbdes:~$ iostat
Linux 3.16.0-44-generic (UBDESPTX) 13/09/15 _x86_64_ (2 CPU)
avg-cpu: %user %nice %system %iowait %steal %idle
5,58 0,15 1,31 0,90 0,00 92,06
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 2,90 47,31 92,93 5141358 10099544
A la pàgina man de iostat s'explica amb detall que vol dir cada camp:
CPU Utilization Report
The first report generated by the iostat command is the CPU Uti‐
lization Report. For multiprocessor systems, the CPU values are
global averages among all processors. The report has the fol‐
lowing format:
%user
Show the percentage of CPU utilization that occurred
while executing at the user level (application).
%nice
Show the percentage of CPU utilization that occurred
while executing at the user level with nice priority.
%system
Show the percentage of CPU utilization that occurred
while executing at the system level (kernel).
%iowait
Show the percentage of time that the CPU or CPUs were
idle during which the system had an outstanding disk I/O
request.
%steal
Show the percentage of time spent in involuntary wait by
the virtual CPU or CPUs while the hypervisor was servic‐
ing another virtual processor.
%idle
Show the percentage of time that the CPU or CPUs were
idle and the system did not have an outstanding disk I/O
request.
Device Utilization Report
The second report generated by the iostat command is the Device
Utilization Report. The device report provides statistics on a
per physical device or partition basis. Block devices and parti‐
tions for which statistics are to be displayed may be entered on
the command line. If no device nor partition is entered, then
statistics are displayed for every device used by the system,
and providing that the kernel maintains statistics for it. If
the ALL keyword is given on the command line, then statistics
are displayed for every device defined by the system, including
those that have never been used. Transfer rates are shown in 1K
blocks by default, unless the environment variable POSIXLY_COR‐
RECT is set, in which case 512-byte blocks are used. The report
may show the following fields, depending on the flags used:
Device:
This column gives the device (or partition) name as
listed in the /dev directory.
tps
Indicate the number of transfers per second that were
issued to the device. A transfer is an I/O request to the
device. Multiple logical requests can be combined into a
single I/O request to the device. A transfer is of inde‐
terminate size.
Blk_read/s (kB_read/s, MB_read/s)
Indicate the amount of data read from the device
expressed in a number of blocks (kilobytes, megabytes)
per second. Blocks are equivalent to sectors and there‐
fore have a size of 512 bytes.
Blk_wrtn/s (kB_wrtn/s, MB_wrtn/s)
Indicate the amount of data written to the device
expressed in a number of blocks (kilobytes, megabytes)
per second.
Blk_read (kB_read, MB_read)
The total number of blocks (kilobytes, megabytes) read.
Blk_wrtn (kB_wrtn, MB_wrtn)
The total number of blocks (kilobytes, megabytes) writ‐
ten.
rrqm/s
The number of read requests merged per second that were
queued to the device.
wrqm/s
The number of write requests merged per second that were
queued to the device.
r/s
The number (after merges) of read requests completed per
second for the device.
w/s
The number (after merges) of write requests completed per
second for the device.
rsec/s (rkB/s, rMB/s)
The number of sectors (kilobytes, megabytes) read from
the device per second.
wsec/s (wkB/s, wMB/s)
The number of sectors (kilobytes, megabytes) written to
the device per second.
avgrq-sz
The average size (in sectors) of the requests that were
issued to the device.
avgqu-sz
The average queue length of the requests that were issued
to the device.
await
The average time (in milliseconds) for I/O requests
issued to the device to be served. This includes the time
spent by the requests in queue and the time spent servic‐
ing them.
r_await
The average time (in milliseconds) for read requests
issued to the device to be served. This includes the time
spent by the requests in queue and the time spent servic‐
ing them.
w_await
The average time (in milliseconds) for write requests
issued to the device to be served. This includes the time
spent by the requests in queue and the time spent servic‐
ing them.
svctm
The average service time (in milliseconds) for I/O
requests that were issued to the device. Warning! Do not
trust this field any more. This field will be removed in
a future sysstat version.
%util
Percentage of CPU time during which I/O requests were
issued to the device (bandwidth utilization for the
device). Device saturation occurs when this value is
close to 100% for devices serving requests serially. But
for devices serving requests in parallel, such as RAID
arrays and modern SSDs, this number does not reflect
their performance limits.
Veure estadísitiques només de CPU:
iostat -c
Veure estadísitiques només de I/O de disc:
iostat -d
Veure estadísitiques d'un dispositiu determinat:
iostat -p sda (indicarem el dispositiu que vulguem)
Veure estadísitiques de LVM:
iostat -N