Shulou(Shulou.com)06/02 Report--

1. Configuration file structure and location

The multipath configuration file / etc/multipath.conf consists of section, sub-section, atribute, value, and so on, and its structure is as follows:

{

...

{

...

}

}

The template of the configuration file is located at / usr/share/doc/device-mapper-multipath-X.Y.Z/multipath.conf by default (Xmai Y _ Z is the actual version number of multipath). When configuring the multipath configuration file, you can copy the file to / etc/multipath.conf

Then, the custom configuration is carried out.

The available section keywords are as follows:

1) defaults: the default setting for global properties.

2) blacklist: blacklist. Multipath ignores devices in the blacklist.

3) blacklist_exceptions: remove the blacklist and add it to the blacklist, but the devices included here will not be ignored.

4) multipaths: multi-path related configuration.

5) devices: storage device-related configuration.

2.defaults section available properties

1) polling_interval: the interval between path checks (in seconds).

2) max_polling_interval: the maximum time interval for path checking, which defaults to 4 times of polling_interval (in seconds).

3) multipath_dir: the path of multi-path shared libraries, which is specific to the system. Default is / lib/multipath or / lib64/multipath.

4) find_multipaths: the default is no, which creates multipath devices for all devices outside the blacklist. If set to yes, multipath devices will be created for three scenarios: the wwid of two paths that are not in the blacklist is the same; the user forces to create them manually; and the wwid of one path is the same as the previously created multipath device.

5) verbosity: the minimum information output level is 0, the highest is 6, and the default is 2.

6) path_selector: path selection algorithm, where "round-robin 0" means to cycle through multiple paths; "queue-length 0" means to select the path with the least number of IO currently processed; and "service-time 0" means to select the path with the shortest IO service time.

7) path_grouping_policy: path grouping policy, where "failover" represents one path and one group (default); "multibus" indicates that all paths are in one group; "group_by_serial" indicates grouping by sequence number; and "group_by_prio" indicates grouping by priority.

"group_by_node_name" means to group by name.

8) uid_attribute: which attribute of udev uniquely identifies a device. The default value is ID_SERIAL.

9) prio: path priority acquisition method, where "const" returns 1 (default); "emc" generates priority for emc array; "alua" generates priority based on SCSI-3 ALUA configuration; "ontap" generates priority for NetAPP array

"rdac" generates priority for LSI/Engenio/NetApp E-Series RDAC controller; "hp_sw" generates priority according to Compaq/HP controller active/standby mode; "hds" generates priority for Hitachi HDS modular array.

"random" randomly generates a priority with a value between 1 and 10; "weightedpath" generates a priority based on the regular expression and the prio_args parameter value.

10) prio_args: calculates the parameters of the priority function.

11) features: specifies the feature that uses Device Mapper, where "queue_if_no_path" indicates that the request will be queued when there is no available path, and "no_partitions" means that kpartx is prohibited from generating partitions.

12) path_checker: path checking method, where "readsector0" indicates that the path state is determined by reading the first sector of the device, which is abandoned and replaced by directio; "tur" means to run the "TEST UNIT READY" command to determine the path state

"emc_clariion" means to execute "EMC Clariion specific EVPD page 0xC0" to determine the status of the path; "hp_sw" means to check the HP Active/Standby array; "rdac" means to check the status of the "LSI/Engenio/NetApp E-Series RDAC" storage controller.

"direction" means to read the first sector of the device with DirectIO.

13) failback: method to restore a path, where "Immediate" indicates immediate recovery to the high priority path group containing the active path; "manual" indicates manual recovery (default); and "followover" indicates recovery only if the first path of the path group is available

"values > 0" indicates delayed recovery.

14) rr_min_io: the number of IO performed before switching to the next path in the current pathgroup, which is only used for the core version number of 2.6.31. The default value is 1000.

15) rr_min_io_rq: the number of IO before switching to the next path in the current path group, which is only used for core version numbers of 2.6.31 and later. The default value is 1.

16) no_path_retry: the number of retries made by the system before the queue is disabled. "fail" indicates that an error is returned directly, "queue" means all join the queue, and the default value is 0.

17) user_friendly_names: if yes, it is named by the setting in / etc/multipath/bindings; if no, wwid is used (which can be overridden by the setting in multipaths). The default value is no.

18) the maximum number of file descriptors that max_fds:multipathd and multipath can open.

19) checker_timeout: timeout for path checking (in seconds). The default value is / sys/block/sd/device/ timeout.

20) fast_io_fail_tmo:SCSI IO error timeout, which should be smaller than dev_loss_tmo. If off, timeout is disabled.

21) the dev_loss_tmo:SCSI device removal timeout is set to 300 by default in Linux (in seconds).

22) queue_without_daemon: if set to no, if multipathd is not started, IO of all devices is prohibited from joining the queue.

23) bindings_file: when user_friendly_names is set, the name binds the path to the file. The default is / etc/multipath/bindings.

24) wwids_file:wwids tracks the file path, which defaults to / etc/multipath/wwids.

25) log_checker_err: the logging method for path checking errors. Default is always.

26) reservation_key: the key specified for the mpathpersist command.

27) retain_attached_hw_handler: whether to continue to use hardware_handler. The default is no.

28) detect_prio: if set to yes, try to use alua detection first. Default is no.

29) hw_str_match: if set to yes, string matching name, manufacturer and other information is preferred. Default is no.

30) force_sync: if set to yes, the path is checked in synchronous mode. Default is no.

31) deferred_remove: if set to yes, the deletion of devices without a path will be delayed. Default is no.

32) config_dir: specify the directory of the configuration file. If it is not "", search for the * .conf files in the directory in alphabetical order and read them as you would with / etc/multipath.conf. The default is / etc/multipath/conf.d.

33) delay_watch_checks: if it is greater than 0, it is considered valid only if the continuous delay_watch_checks check path is valid. The default is no.

34) delay_wait_checks: if it is greater than 0, the delay_watch_check check is valid and the delay_wait_checks check is delayed before it is officially re-enabled. The default is no.

35) missing_uev_msg_delay: when a new device is created, the udev message is accepted after a delay of missing_uev_msg_delay seconds. The default is 30.

3.blacklist configuration

Devices in blacklist will be ignored by multipath. There are three formats:

1) the WWID of the device followed by the wwid

2) regular expression of devnode followed by device name

3) device device description, which is a Subsection, which needs to include vendor and product. For more information, please see the description of devices section.

The blacklist_exceptions syntax is the same as blacklist, which means to cancel the ignore of devices in blacklist.

4.multipaths configuration

Multipaths configures a single path separately, and each path uses a separate multipath sub-section, which can contain the following attributes:

1) wwid: path WWID (required), which can be obtained using the command / lib/udev/scsi_id-g-u / dev/sdX.

2) alias: device alias.

3) path_grouping_policy

4) path_selector

5) prio

6) prio_args

7) failback

8) rr_weight

9) flush_on_last_del

10) no_path_retry

11) rr_min_io

12) rr_min_io_q

13) features

14) reservation_key

15) deferred_remove

16) delay_watch_checks

17) delay_wait_checks

5.devices configuration

Each device subsection in the devices section is used to describe a device, and its main properties are as follows:

1) vendor: manufacturer (required).

2) product: product model.

3) revision: version number.

4) product_blacklist: blacklist of product models.

5) alias_prefix: device name prefix, default is mapth.

6) hardware_handler: models of hardware-related operations, including:

Emc: Hardware handler for EMC storage arrays.

Rdac: Hardware handler for LSI/Engenio/NetApp E-Series RDAC storage controller.

Hp_sw: Hardware handler for Compaq/HP storage arrays in active/standby mode.

Alua: Hardware handler for SCSI-3 ALUA compatible arrays.

7) the instructions under path_grouping_policy are the same as those described in the defaults section.

8) uid_attribute

9) path_selector

10) path_checker

11) prio

12) prio_args

13) features

14) failback

15) rr_weight

16) no_path_retry

17) rr_min_io

18) rr_min_io_rq

19) fast_io_fail_tmo

20) dev_loss_tmo

21) flush_on_last_del

22) retain_attached_hw_handler

23) detect_prio

24) deferred_remove

25) delay_watch_checks

16) delay_wait_checks

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