User`s guide

46 Implementing an Open IBM SAN

maxphys

This parameter specifies the maximum number of bytes you can transfer for

each SCSI transaction. The default value is 126976 (124 KB). If the I/O block

size that you requested exceeds the default value, the request is broken into

more than one request. The value should be tuned to the intended use and

application requirements. For maximum bandwidth set the maxphys

parameter by adding the following line to the /etc/system file:

set maxphys=8388608

If you are using Veritas volume manager on the ESS LUNs, you must set the

VxVM max I/O size parameter (vol_maxio) to match the maxphys parameter.

If you set the maxphys parameter to 8388608, add the following line to the

/etc/system file to also set the VxVM I/O size to 8 MB:

set vxio:vol_maxio=16384

Emulex or QLogic adapters

The following sections contain the procedures to set the Sun host system

parameters for optimum performance on the ESS with the Emulex adapter:

1. Type cd /etc to change to the /etc subdirectory.

2. Back up the system file in the subdirectory.

3. Edit the system file and set the following parameters for servers with

configurations that only use Emulex adapters.

sd_io_time

This parameter specifies the timeout value for disk operations. Add the

following line to the /etc/system file to set the sd_io_time parameter for the

ESS LUNs:

set sd:sd:_io_time=0x78

sd_retry_count

This parameter specifies the retrycount for disk operations. Add the following

line to the /etc/system file to set the sd_retry_count parameter for the ESS

LUNs: