EMC Qlogic QLA22xx Installationsanleitung PDF herunterladen (Seite 24)

Symmetrix Fibre Channel with Qlogic HBAs on Linux Hosts

Arbitrated Loop Configurations

Additional Notes Dynamic Device Reconfiguration

Linux currently lacks a command built into the kernel that allows for

a dynamic SCSI channel reconfiguration like drvconfig or ioscan.

Depending upon the hardware configuration and on whether the

QLogic driver has been loaded into the kernel as a module, the

QLogic driver can be unloaded and then reloaded. If the QLogic

driver has been loaded as a module, this unloading and reloading

will cause a scan of the SCSI bus. The driver should detect the newly

added device(s). If the QLogic driver is loaded into the kernel

statically, the system will need to be rebooted in order for the devices

to be detected reliably.

The modprobe command is a wrapper or an extension to insmod. It

uses and maintains a set of files that describe all the modules that are

available for the current kernel in /lib/modules. modprobe can be

used to load and unload an entire set of modules in addition to just a

single module. Both the loading and unloading of the QLogic

modular driver is done with modprobe.

The unloading of the module is done with modprobe -r

qla2x00(smp). modprobe with the -r switch used to unload the

loadable modules from the running kernel if they are not in use and if

other modules are not dependent upon them.

In the standard Linux v2.2.x kernel, the SCSI addresses are not used

in the device names as they are in other types of UNIX (Sun, SGI,

HP-UX, and BSD, for example). Block device filenames take the form

/dev/sdln, where l is the letter denoting the physical drive and n is

the number denoting the partition on that physical drive. Device

names and minor numbers are assigned dynamically at boot time or

device loading time in the order of discovery.

Depending upon the hardware configuration, if a device is added

and the system rebooted, the device numbering can and will change.

This change makes the host’s mount table inaccurate. For the most

consistent results and to reduce the possibility of mount table

inaccuracies, new devices should be appended to the list of already

attached devices. For example, if the host contains multiple HBAs, it

would be best to append the new device to the last HBA and to the

end of the device list attached to that HBA. This would eliminate the

need to alter the pre-existing entries in the mount table, since the new

device could be appended to that as well. If a new device were added

to the first out of two HBAs and the system rebooted, the devices

would all shift by one number and the mount table entries would

also need to be shifted by one device. If there is only one HBA, the

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