Configuring device I/O processing time

You can reduce the time that is needed to complete jobs that have substantial I/O by changing the device database file.

Before you begin

You can shorten the processing time of large I/O directed to one disk array unit by completing the two procedures that are described in Procedure A and Procedure B. Both procedures must be completed for this operation to be successful.

Procedure A

About this task

Procedure A applies to Tru64 UNIX version 4.0 and later. For more information, see the Tru64 UNIX ddr.dbase and ddr_config manual files.

Complete the following steps to set up the Tru64 UNIX device parameter database for features that are specific to the system.

Procedure

Quiesce the storage.
Place the host system in single-user mode as root.

Edit the /etc/ddr.dbase file by including the following lines as an entry in the DISKS subsection:

SCSIDEVICE
    #
    # Values for the IBM 2076 [2145]
    #
    Type = disk
    Name = "IBM" "2145"
    #
    PARAMETERS:
        TypeSubClass        = hard_disk, raid
        BadBlockRecovery    = disabled
        DynamicGeometry     = true
        LongTimeoutRetry    = enabled
        PwrMgmt_Capable     = false
        TagQueueDepth       = 20
        ReadyTimeSeconds    = 180
        CMD_WriteVerify     = supported
        InquiryLength       = 255
        RequestSenseLength  = 255

Compile the ddr.dbase file by issuing the following command:
ddr_config –c
Confirm the values by issuing the following command:
ddr_config –s disk "IBM" "2076"

Procedure B

About this task

Procedure B requires a kernel rebuild.

Complete the following steps to set a kernel SCSI parameter:

Procedure

Quiesce the storage.
Place the host system in single-user mode as root.
Edit the /sys/data/cam_data.c file by changing the non-read/write command timeout values in the changeable disk driver timeout section.

Change from u_long cdisk_to_def = 10; /* 10 seconds */ to u_long cdisk_to_def = 60; /* 60 seconds */

Compile the cam_data.c file by issuing the following command:

doconfig –c hostname

Where hostname is the name of the system kernel that can be found in the /sys/conf/ directory.

The following example shows output from the –c hostname command:

#doconfig -c "ES47"
*** KERNEL CONFIGURATION AND BUILD PROCEDURE ***

Saving /sys/conf/ES47 as /sys/conf/ES47.bck

Do you want to edit the configuration file? (y/n) [n]: y

Using ed to edit the configuration file.  Press return when ready,
or type 'quit' to skip the editing session: quit


*** PERFORMING KERNEL BUILD ***
Working....Wed Mar 22 17:36:19 PST 2006

The new kernel is /sys/ES47/vmunix
#