Dell PowerVault MD3600i El manual del propietario descargar pdf (Pagina 204)

204 Configuration: Device Mapper Multipath for Linux

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, 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

occur automatically 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.

rescan_dm_devs Dell provided script. Forces a rescan of the host SCSI bus

and aggregates multipathing devices as needed. For use

when:

• LUNs are dynamically mapped to the hosts.

• New targets are added to the host.

• Failback of the storage array is required.

• For MD3600i Series arrays, iSCSI sessions have to be

established for rescan to take effect.

Table 14-1. Useful Device Mapper Commands

(continued)

Command Description

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Dell PowerVault MD3600i El manual del propietario Pagina 204