Getting Information About DRBD Options

This article describes different ways to get information such as default values, units of measurement, and accepted value ranges, for DRBD® configuration file options.

If you are using DRBD 9, you can use the man drbd.conf-9.0 command to get detailed information about options that you can use within DRBD configuration files.

An example entry from the manual page for the ping interval option is:

ping-int interval

    When the TCP/IP connection to a peer is idle for more than
ping-int seconds, DRBD will send a keep-alive packet to make
sure that a failed peer or network connection is detected
reasonably soon. The default value is 10 seconds, with a
minimum of 1 and a maximum of 120 seconds. The unit is seconds.

Another way that you can get information, such as default values, value ranges, and units of measurement, for DRBD options, is by using the drbdsetup command.

The drbdsetup xml-help command is used to generate output for manual pages. You can use it as an alternative way to see information about DRBD options, in XML format. This can be useful if you want to quickly get default values, units of measurement, and value ranges, for DRBD options, without having to examine surrounding text in the manual page. However, this way will not show you the context for using DRBD options that the manual page might show.

The xml-help command is available for the following types of DRBD configuration file options:

# drbdsetup xml-help resource-options
# drbdsetup xml-help peer-device-options
# drbdsetup xml-help net-options
# drbdsetup xml-help disk-options

For example:

# drbdsetup xml-help net-options
[...]
<option name=ping-int type=numeric>
        <min>1</min>
        <max>120</max>
        <default>10</default>
        <unit_prefix>1</unit_prefix>
        <unit>seconds</unit>
</option>
[...]

If you have already configured a DRBD resource, either manually or by using LINSTOR®, you can get the resource’s DRBD options values by using the drbdsetup show --show-defaults command. You can run the command and add a configured DRBD resource’s name as an argument to show the resource’s running configuration, including DRBD options and their default values (if the options were not specified in the DRBD configuration file itself). If you enter the command without specifying a DRBD resource, then the command will show configuration files for all configured DRBD resources on the node.

This command is useful to learn which DRBD options are implicitly configured along with their default values. The command output will also show in which section of the DRBD configuration file options occur: options (global*)*, disk, or net. Unlike the other ways of getting DRBD options information mentioned in this article, the drbdsetup show --show-defaults will not show the range of acceptable values for the DRBD options.

For example:

# drbdsetup show --show-defaults testres
resource testres {
    options {
        cpu-mask                ; # default
        on-no-data-accessible   io-error; # default
        auto-promote            yes; # default
        peer-ack-window         4096s; # bytes, default
        peer-ack-delay          100; # milliseconds, default
        twopc-timeout           300; # 1/10 seconds, default
        twopc-retry-timeout     1; # 1/10 seconds, default
        auto-promote-timeout    20; # 1/10 seconds, default
        max-io-depth            8000; # default
        quorum                  majority;
        on-no-quorum            io-error;
        quorum-minimum-redundancy       off; # default
        on-suspended-primary-outdated   disconnect; # default
    }
    _this_host {
        node-id                 0;
        volume 0 {
            device                      minor 1000;
            disk                        /dev/drbdpool/testres_00000;
            meta-disk                   internal;
            disk {
                size                    0s; # bytes, default
                on-io-error             detach; # default
                disk-barrier            no; # default
                disk-flushes            yes; # default
                disk-drain              yes; # default
                md-flushes              yes; # default
    [...]
    }
    [...]
}

If you are using LINSTOR, you can use the output from the linstor <LINSTOR_object> drbd-options --help (or drbd-peer-options --help) command to get information about DRBD options.

For example:

# linstor resource-definition drbd-options --help
[...]
--ping-int PING_INT   Range: [1, 120]; Default: 10; Unit: seconds
[...]

💡 TIP: The command linstor <LINSTOR_object> opt --help shows the same output as linstor <LINSTOR_object> drbd-options --help, if you are interested in saving some keystrokes.

For the LINSTOR --help and the drbdsetup commands, it is useful to pipe the output through the less command. You can then use the forward slash key (/) to search for keywords to find the DRBD option that you are interested in.

Created by MAT, 2023-03-13

Reviewed by DJV 2023-03-14