Setting the Sun host parameters for use with IBM® SDD and VERITAS DMP

You can set the parameters on the Sun host to optimize the performance between the HBA and the SAN Volume Controller.

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 use the HBA:

   sd_max_throttle

   The sd_max_throttle parameter specifies the maximum number of commands that the sd driver can queue to the host adapter driver. The default value is 256, but you must set the parameter to a value less than or equal to a maximum queue depth for each LUN that is connected. Determine the value by using the following formula:

   256 ÷ (LUNs per adapter)

   where LUNs per adapter is the largest number of LUNs assigned to a single adapter.

   To set the sd_max_throttle parameter for the SAN Volume Controller LUNs in this example, you would add the following line to the /etc/system file:

   set sd:sd_max_throttle=5

   sd_io_time

   This parameter specifies the time-out value for disk operations. Add the following line to the /etc/system file to set the sd_io_time parameter for the SAN Volume Controller LUNs:

   set sd:sd_io_time=0x78

   sd_retry_count

   This parameter specifies the retry count for disk operations. Add the following line to the /etc/system file to set the sd_retry_count parameter for the SAN Volume Controller LUNs:

   set sd:sd_retry_count=5

   maxphys

   This parameter specifies the maximum number of bytes that 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 for the application requirements. For maximum bandwidth, set the maxphys parameter by adding the following line to the /etc/system file:

   set maxphys=1048576 (1 MB)

   Note: Do not set the value for maxphys greater than 1048576 (1 MB). Doing so can cause the system to hang.

   If you are using the VERITAS Volume Manager on the SAN Volume Controller LUNs, you must set the VxVM maximum I/O size parameter (vol_maxio) to match the maxphys parameter. When you set the maxphys parameter to 1048576 and you use the VERITAS Volume Manager on your SAN Volume Controller LUNs, set the maxphys parameter like in the following sentence:

   set vxio:vol_maxio=2048

   Note: The unit for vxio:vol_maxio is disk block (1/2 KB).