This appendix discusses the following:
This section discusses the following:
SGI recommends that you use the same settings on all applicable nodes in the cluster.
 | Note: Before changing any parameter, you should understand the ramifications
of doing so on your system. You should change debugging parameters only
at the recommendation of SGI Support.
The values of these parameters vary in different releases of the product. When upgrading the product, consult SGI Support to determine whether any changes made to the parameters in this chapter should be carried forward. Setting these parameters incorrectly may render the system unstable or otherwise unusable. |
You can set a parameter permanently across reboots by adding it to the /etc/modprobe.d/sgi-cxfs-xvm.conf file. Use the following format:
options module systune=value |
where:
module is one of the following:
sgi-pm sgi-xvm The section that describes a parameter lists the module name.
systune is the parameter name, such as xvm_congestion_check
value is the value you want to set for the parameter, such as 2
| Note: Do not use spaces around the = character. |
There should be only one options line per module; if you want to specify multiple parameters, you must place them all on that single line.
For example, to permanently set the xvm_congestion_check parameter (which is in the xvm module) to 1, add the following line to /etc/modprobe.d/sgi-cxfs-xvm.conf :
options sgi-xvm xvm_congestion_check=1 |
The change will take effect upon reboot.
For a temporary change to a dynamic parameter, use the Linux sysctl(8) command as follows:
# sysctl prefix.systune=value |
where:
prefix is one of the following:
dev.pathmgr dev.xvm systune is the parameter name, such as xvm_congestion_check
value is the value you want to set for the parameter, such as 1
| Note: Do not use spaces around the = character. |
For example, to temporarily set the xvm_congestion_check parameter (which has the dev.xvm prefix) to 1, enter the following:
# sysctl dev.xvm.xvm_congestion_check=1 dev.xvm.xvm_congestion_check = 1 |
To query the current setting of a parameter, use the Linux sysctl(8) command:
# sysctl prefix.systune |
where:
prefix is one of the following:
dev.pathmgr dev.xvm systune is the parameter name, such as xvm_congestion_check
For example, to query the current setting of the xvm_congestion_check parameter (which has the dev.xvm prefix):
# sysctl dev.xvm.xvm_congestion_check dev.xvm.xvm_congestion_check = 1 |
Static parameters require a reboot to take affect. This section discusses the following:
Specifies whether XVM passes the stripe unit or the hardware sector size to XFS or another user via the queue limits field min_io.
Range of values:
0 causes min_io to pass the stripe unit (default)
1 causes min_io to pass the hardware sector size
Prefix: dev.xvm
Module: sgi-xvm
Specifies whether or not a congestion query from the filesystem will propagate to all LUNs that make up the XVM volume.
Range of values:
0 disables congestion queries (default)
1 enables congestion queries
Caution: Enabling congestion check can negatively impact I/O performance.
Prefix: dev.xvm
Module: sgi-xvm
Specifies the data throughput per thread using central memory. Increasing this parameter may decrease performance of other jobs running on the system.
Range of values:
Default: 5
Minimum: 1
Maximum 10
Prefix: dev.xvm
Module: sgi-xvm
Specifies the number of parallel I/O processes used in reviving mirrors. Increasing this parameter may decrease the I/O performance of other tasks on the system.
Range of values:
Default: 4
Minimum: 1
Maximum 12
Prefix: dev.xvm
Module: sgi-xvm
Defines the maximum number of mirror daemons started for processing mirror retries and mirror completions that cannot be done from completion threads.
| Caution: Adjusting the values can keep more threads alive in the pool rather than spawning and exiting threads, which can cause performance issues. |
Range of values:
Default: 25
Minimum: 0
Maximum: 255
Prefix: dev.xvm
Module: sgi-xvm
Defines the minimum number of mirror daemons started for processing mirror retries and mirror completions that cannot be done from completion threads.
| Caution: Adjusting the values can keep more threads alive in the pool rather than spawning and exiting threads, which can cause performance issues. |
Range of values:
Default: 1
Minimum: 0
Maximum: 255
Prefix: dev.xvm
Module: sgi-xvm
Dynamic parameters take affect as soon as they are changed. This section discusses the following:
(Linux systems only) Specifies whether or not recent I/O activity (the amount of data transferred and the number of I/O operations for a 1-second period) is reported in the output of the xvm show command. The information is reported using the following format:
[ nnn KB nnn ops] |
| Note: Enabling this parameter will decrease throughput (IOPs/second) by a small percentage. Therefore, you should enable it only as a configuration aid and disable it for production use. |
Range of values:
0 disables the report of I/O activity in the show output (default)
1 enables the report of I/O activity in the show output
Prefix: dev.pathmgr
Module: sgi-pm
| Note: This parameter has an effect only on NUMAlink systems such as SGI UV or SGI UV 2000. |
Specifies the number of bytes of I/O data below which the I/O is directed to a path close to the issuing thread, rather than a path close to the data.
Range of values:
Default: 32768
Minimum: 0
Maximum: 1073741824
Prefix: dev.pathmgr
Module: sgi-pm