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4.3. Configuration File Defaults
The
/etc/multipath.conf
configuration file includes a defaults
section that sets the user_friendly_names
parameter to yes
, as follows.
defaults { user_friendly_names yes }
This overwrites the default value of the
user_friendly_names
parameter.
The configuration file includes a template of configuration defaults. This section is commented out, as follows.
#defaults { # udev_dir /dev # polling_interval 5 # path_selector "round-robin 0" # path_grouping_policy failover # getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n" # prio const # path_checker directio # rr_min_io 1000 # rr_weight uniform # failback manual # no_path_retry fail # user_friendly_names no #}
To overwrite the default value for any of the configuration parameters, you can copy the relevant line from this template into the
defaults
section and uncomment it. For example, to overwrite the path_grouping_policy
parameter so that it is multibus
rather than the default value of failover
, copy the appropriate line from the template to the initial defaults
section of the configuration file, and uncomment it, as follows.
defaults { user_friendly_names yes path_grouping_policy multibus }
Table 4.1, “Multipath Configuration Defaults” describes the attributes that are set in the
defaults
section of the multipath.conf
configuration file. These values are used by DM-Multipath unless they are overwritten by the attributes specified in the devices
and multipaths
sections of the multipath.conf
file.
Note
As of the Red Hat Enterprise Linux 6.0 release, the
mode
, uid
, and gid
parameters have been deprecated. Permissions for device-mapper devices (including mulitpath mappings) are set by means of udev
rules. There is a template file in /usr/share/doc/device-mapper-version
called 12-dm-permissions.rules
which you can use and place in the /etc/udev/rules.d
directory for it to take effect.
Table 4.1. Multipath Configuration Defaults
Attribute | Description | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
polling_interval | Specifies the interval between two path checks in seconds. For properly functioning paths, the interval between checks will gradually increase to (4 * polling_interval ). The default value is 5. | ||||||||||
udev_dir | The directory where udev device nodes are created. The default value is /dev . | ||||||||||
multipath_dir | The directory where the dynamic shared objects are stored. The default value is system dependent, commonly /lib/multipath . | ||||||||||
find_multipaths |
| ||||||||||
verbosity | The default verbosity. Higher values increase the verbosity level. Valid levels are between 0 and 6. The default value is 2 . | ||||||||||
path_selector |
| ||||||||||
path_grouping_policy |
| ||||||||||
getuid_callout |
| ||||||||||
prio |
| ||||||||||
features |
| ||||||||||
path_checker |
| ||||||||||
failback |
| ||||||||||
rr_min_io | Specifies the number of I/O requests to route to a path before switching to the next path in the current path group. This setting is only for systems running kernels older than 2.6.31. Newer systems should use rr_min_io_rq . The default value is 1000. | ||||||||||
rr_min_io_rq | Specifies the number of I/O requests to route to a path before switching to the next path in the current path group, using request-based device-mapper-multipath. This setting should be used on systems running current kernels. On systems running kernels older than 2.6.31, use rr_min_io . The default value is 1. | ||||||||||
rr_weight | If set to priorities , then instead of sending rr_min_io requests to a path before calling path_selector to choose the next path, the number of requests to send is determined by rr_min_io times the path's priority, as determined by the prio function. If set to uniform , all path weights are equal. The default value is uniform . | ||||||||||
no_path_retry |
| ||||||||||
user_friendly_names | If set to yes , specifies that the system should use the /etc/multipath/bindings file to assign a persistent and unique alias to the multipath, in the form of mpath n . If set to no , specifies that the system should use the WWID as the alias for the multipath. In either case, what is specified here will be overridden by any device-specific aliases you specify in the multipaths section of the configuration file. The default value is no . | ||||||||||
queue_without_daemon | If set to no , the multipathd daemon will disable queuing for all devices when it is shut down. The default value is no . | ||||||||||
flush_on_last_del | If set to yes , the multipathd daemon will disable queuing when the last path to a device has been deleted. The default value is no . | ||||||||||
max_fds | Sets the maximum number of open file descriptors that can be opened by multipath and the multipathd daemon. This is equivalent to the ulimit -n command. As of the Red Hat Enterprise Linux 6.3 release, the default value is max , which sets this to the system limit from /proc/sys/fs/nr_open . For earlier releases, if this is not set the maximum number of open file descriptors is taken from the calling process; it is usually 1024. To be safe, this should be set to the maximum number of paths plus 32, if that number is greater than 1024. | ||||||||||
checker_timeout | The timeout to use for prioritizers and path checkers that issue SCSI commands with an explicit timeout, in seconds. The default value is taken from sys/block/sdx/device/timeout . | ||||||||||
fast_io_fail_tmo | The number of seconds the SCSI layer will wait after a problem has been detected on an FC remote port before failing I/O to devices on that remote port. This value should be smaller than the value of dev_loss_tmo . Setting this to off will disable the timeout. The default value is determined by the OS. | ||||||||||
dev_loss_tmo | The number of seconds the SCSI layer will wait after a problem has been detected on an FC remote port before removing it from the system. Setting this to infinity will set this to 2147483647 seconds, or 68 years. The default value is determined by the OS. | ||||||||||
hwtable_regex_match |
| ||||||||||
retain_attached_hw_handler | (Red Hat Enterprise Linux Release 6.4 and later) If this parameter is set to yes and the scsi layer has already attached a hardware handler to the path device, multipath will not force the device to use the hardware_handler specified by the multipath.conf file. If the scsi layer has not attached a hardware handler, multipath will continue to use its configured hardware handler as usual. The default value is no . | ||||||||||
detect_prio | (Red Hat Enterprise Linux Release 6.4 and later) If this is set to yes , multipath will first check if the device supports ALUA, and if so it will automatically assign the device the alua prioritizer. If the device does not support ALUA, it will determine the prioritizer as it always does. The default value is no . | ||||||||||
replace_wwid_whitespace | (Red Hat Enterprise Linux Release 6.5 and later) If this is set to yes , the default getuid_callout for all devices that use this parameter will be changed to include --replace-whitespace . | ||||||||||
reload_readwrite | (Red Hat Enterprise Linux Release 6.5 and later) If this is set to yes , the multipathd daemon will listen to path device change events and if a device has become read/write it will reload the multipath device. | ||||||||||
force_sync | (Red Hat Enterprise Linux Release 6.6 and later) If this is set to "yes", it prevents path checkers from running in async mode. | ||||||||||
delay_watch_checks | (Red Hat Enterprise Linux Release 6.7 and later) If set to a value greater than 0, the multipathd daemon will watch paths that have recently become valid for the specified number of checks. If they fail again while they are being watched, when they next become valid they will not be used until they have stayed up for the number of consecutive checks specified with delay_wait_checks . This allows you to keep paths that may be unreliable from immediately being put back into use as soon as they come back online. The default value is no . | ||||||||||
delay_wait_checks | (Red Hat Enterprise Linux Release 6.7 and later) If set to a value greater than 0, when a device that has recently come back online fails again within the number of checks specified with delay_watch_checks , the next time it comes back online it will be marked and delayed and it will not be used until it has passed the number of checks specified in delay_wait_checks . The default value is no . | ||||||||||
config_dir | (Red Hat Enterprise Linux Release 6.7 and later) If set to anything other than "" , multipath will search this directory alphabetically for files ending in ".conf" and it will read configuration information from them, just as if the information were in the /etc/multipath.conf file. This allows you to have one main configuration that you share between machines in addition to a separate machine-specific configuration file or files. The config_dir parameter must either be "" or a fully qualified directory name. This parameter can be set only in the main /etc/multipath.conf file and not in one of the files specified in the config_dir file itself. The default value is /etc/multipath/conf.d . | ||||||||||
log_checker_err | If set to once , multipathd logs the first path checker error at verbosity level 2. Any later errors are logged at verbosity level 3 until the device is restored. If it is set to always , multipathd always logs the path checker error at verbosity level 2. The default value is always . | ||||||||||
skip_kpartx | (Red Hat Enterprise Linux Release 6.9 and later) If set to yes , kpartx will not automatically create partitions on the device. This allows users to create a multipath device without creating partitions, even if the device has a partition table. The default value of this option is no . | ||||||||||
max_sectors_kb | (Red Hat Enterprise Linux Release 6.9 and later) Sets the max_sectors_kb device queue parameter to the specified value on all underlying paths of a multipath device before the multipath device is first activated. When a multipath device is created, the device inherits the max_sectors_kb value from the path devices. Manually raising this value for the multipath device or lowering this value for the path devices can cause multipath to create I/O operations larger than the path devices allow. Using the max_sectors_kb parameter is an easy way to set these values before a multipath device is created on top of the path devices and prevent invalid-sized I/O operations from being passed. If this parameter is not set by the user, the path devices have it set by their device driver, and the multipath device inherits it from the path devices. |