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Oracle Tips by Burleson |
Disk I/O Tuning
Chapter 3:
Tuning SCSI Under UNIX
For
some hardware RAIDs, it has been found that decreasing
sd_max_throttle improved performance due to better load balancing
among LUNs. It might be worth a shot if your hardware based RAID
system seems sluggish.
There
are several additional host configuration variables that can be
specified in addition to sd_max_throttle and in relation to the SCSI
interface on SUN Solaris. These are usually specified in the
/etc/system file as was shown above.
The
following variables in the /etc/systems file should be set to
maximize system performance. When any of these variables are
changed, the system must be rebooted for changes to take effect.
sd_max_throttle
-- The sd_max_throttle variable sets the maximum number of commands
that the SCSI sd driver will attempt to queue to a single HBA
driver. The default value is 256. This variable must be set to a
value less than or equal to the maximum queue depth of each LUN
connected to each instance of the sd driver. If this is not done,
then commands may be rejected because of a full queue condition and
the sd driver instance that receives the queue full message will
throttle down sd_max_throttle to 1. This obviously will result in
degraded performance. The variable is set in the /etc/system file
as follows:
set sd:sd_max_throttle=20
The above text is
an excerpt from:
Oracle Disk I/O Tuning
Disk IO Performance & Optimization for Oracle
Databases
ISBN
0-9745993-4-4
by Mike Ault
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