EMC Qlogic QLA22xx Guide d'installation télécharger pdf (Page 61)

Symmetrix Fibre Channel with Qlogic HBAs on Linux Hosts

Fabric Configurations

Edit sg.h

The value for the SCSI generic buffer must be increased. Change to

the appropriate directory and increase the value for

SG_SCATTER_SZ to the maximum of 131072.

cd /usr/src/linux/include/scsi

vi sg.h

Around line 195, look for the following code block:

Change the value for SG_SCATTER_SZ (8* 4096) to (32 * 4096).

After the kernel compilation and system reboot, using the following

command can validate this change:

cat /proc/sys/kernel/sg-big-buff

Proceed to Configuring and Compiling the Kernel on page 64 to compile

the Linux kernel.

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.

#define SG_SCATTER_SZ (8 * 4096) /* PAGE_SIZE not available to user */

/* Largest size (in bytes) a single scatter-gather list element can have.

The value must be a power of 2 and <= (PAGE_SIZE * 32) [131072 bytes on

i386]. The minimum value is PAGE_SIZE. If scatter-gather not supported

by adapter then this value is the largest data block that can be

read/written by a single scsi command. The user can find the value of

PAGE_SIZE by calling getpagesize() defined in unistd.h . */

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EMC Qlogic QLA22xx Guide d'installation Page 61