.. _disk:

Disk I/O

.. image:: ../_static/diskio.png

Glances displays the disk I/O throughput, count and mean latency:

bytes per second (default behavior / Bytes/s, KBytes/s, MBytes/s, etc)
requests per second (using --diskio-iops option or B hotkey)
mean latency (using --diskio-latency option or L hotkey)

It's also possible to define:

a list of disk to show (white list)
a list of disks to hide
aliases for disk name (use \ to espace special characters)

under the [diskio] section in the configuration file.

For example, if you want to hide the loopback disks (loop0, loop1, ...) and the specific sda5 partition:

.. code-block:: ini

[diskio]
hide=sda5,loop.*

or another example:

.. code-block:: ini

[diskio]
show=sda.*

Filtering is based on regular expression. Please be sure that your regular expression works as expected. You can use an online tool like regex101_ in order to test your regular expression.

.. note::

When a disk has an ``alias`` defined, the ``hide`` and ``show`` patterns
are evaluated against **both** the original device name and its alias,
and the disk is hidden (or shown) if **either** matches. This means a
"negative-lookahead" allow-list pattern such as
``hide=^(?!(?:nvme[0-9]+n[0-9]+$|sd[a-z]+$)).*`` will inadvertently match
aliases that do not follow the device naming scheme (e.g. ``my_data_disk``)
and therefore hide every aliased disk. Prefer ``show=`` for allow-list
semantics, or write explicit ``hide=`` patterns that target the names you
actually want to exclude.

It is also possible to define thesholds for latency and bytes read and write per second:

.. code-block:: ini

[diskio]
# Alias for sda1 and sdb1
#alias=sda1:SystemDisk,sdb1:DataDisk
# Default latency thresholds (in ms) (rx = read / tx = write)
rx_latency_careful=10
rx_latency_warning=20
rx_latency_critical=50
tx_latency_careful=10
tx_latency_warning=20
tx_latency_critical=50
# Set thresholds (in bytes per second) for a given disk name (rx = read / tx = write)
dm-0_rx_careful=4000000000
dm-0_rx_warning=5000000000
dm-0_rx_critical=6000000000
dm-0_rx_log=True
dm-0_tx_careful=700000000
dm-0_tx_warning=900000000
dm-0_tx_critical=1000000000
dm-0_tx_log=True

You also can automatically hide disk with no read or write using the hide_zero configuration key. The optional hide_threshold_bytes option can also be used to set a threshold higher than zero.

.. code-block:: ini

[diskio]
hide_zero=True
hide_threshold_bytes=0

.. _regex101: https://regex101.com/