Hitachi USP V, Configuration Manual, Page: 48 / 70

3-6 Configuring the New Disk Devices
Hitachi Universal Storage Platform V/VM Configuration Guide for SGI
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IRIX
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Host Attachment
Enabling Command Tag Queuing
Command tag queuing (CTQ) must be enabled to optimize the performance of
the USP V devices. Since CTQ is disabled by default in IRIX systems, you need
to enable it and set the queue depth for each USP V logical device using the fx
utility. Table 3-1 lists the queue depth requirements for the USP V devices.
Table 3-1 Queue Depth Requirements for the USP V Devices
Parameter Required Value
Queue depth per LU ≤ 32
Queue depth per port ≤ 1024
Note: You can adjust the queue depth for the USP V devices later as needed
(within the specified range) to optimize the I/O performance of the USP V
devices. If I/O response time will be long, you must adjust queue depth
parameter. You can check the response time using the sar command (see
Figure 3-4 ) and set queue depth within 10 seconds.
sgi 1# sar –d 1 10
Å
Input sar command.
IRIX64 sgi 6.5-ALPHA-1276737220 09080737 IP27 10/17/00
11:01:02 device %busy avque r+w/s blks/s w/s wblks/s avwait avserv
Å
Response
11:01:03 dks0d1 0 0.0 0.0 0 0.0 0 0.0 0.0 time (msec)
dks0d6 0 0.0 0.0 0 0.0 0 0.0 0.0
dks14d0 100 4.0 2.0 133 2.0 133 1745.0 290.0
dks14d0l1 100 5.5 3.9 500 1.0 125 1117.5 285.0
dks14d0l2 100 4.5 2.0 250 0.0 0 955.0 510.0
dks14d0l3 100 5.2 3.9 2219 1.0 2 1735.0 255.0
dks14d0l4 100 5.7 2.9 252 1.0 2 963.3 276.7
dks14d0l5 100 5.0 2.0 250 0.0 0 1585.0 370.0
Figure 3-4 Checking the I/O Response Time Using the Sar Command
To enable CTQ and set the queue depth for the USP V devices (see Figure 3-
5 ):
1. Start the fx disk utility and select the desired device to configure.
2. Once the device is selected and the fx> prompt reappears, enter
/label/set/para to set the command tag queuing and queue depth
options.
3. When prompted, enter enable to enable CTQ and enter the desired CTQ
depth (e.g., 32).
4. When prompted, enter yes to modify the drive parameters as specified.
5. Exit the fx utility and enter yes to write out (save) the changes to the
drive parameters.
6. Repeat steps 1 through 5 for each new USP V disk device.