Dell PowerVault MD3220 Bedienungsanleitung PDF herunterladen (Seite 187)

Configuration: Device Mapper Multipath for Linux 187

Limitations and Known Issues

• In certain error conditions with the no_path_retry or the

queue_if_no_path feature is set, applications may hang. To overcome

these conditions the you must enter the following command for each

affected multipath device:

dmsetup message [device] 0 "fail_if_no_path"

where

[device]

is the multipath device name (for example. mpath2; do

not specify the path)

• I/O may hang when a Device Mapper device is deleted before the volume

is unmounted.

• If the scsi_dh_rdac module is not included in initrd, slower device

discovery may be seen and the syslog may become populated with buffer

I/O error messages.

• I/O may hang if the host server or storage array is rebooted while I/O is

active. All I/O to the storage array must be stopped before shutting down

or rebooting the host server or storage array.

• After a failed path is restored on an MD3600i Series array, failback does not

automatically occur because the driver cannot auto-detect devices without

a forced rescan. Run the command

rescan_dm_devs

to force a rescan

of the host server. This restores the failed paths enabling failback to occur.

• Failback can be slow when the host system is experiencing heavy I/O. The

problem is exacerbated if the host server is also experiencing very high

processor utilization.

• The Device Mapper Multipath service can be slow when the host system is

experiencing heavy I/O. The problem is exacerbated if the host server also

experiences very high processor utilization.

• If the root disk is not blacklisted in the multipath.conf file, a multipathing

node may be created for the root disk. The command

multipath –ll

lists vendor/product ID which can help identify this issue.

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Dell PowerVault MD3220 Bedienungsanleitung Seite 187