rpvutil Command

Purpose

Configures a mirror pool in the remote physical volume (RPV) client of Geographic Logical Volume Manager (GLVM).

Syntax

rpvutil -h [tunable_name]
rpvutil [-v vg_name] {-a | -o tunable_name[=value] | -c}
rpvutil -d tunable_name
rpvutil -s rpvs_name
rpvutil -r rpvs_name

Description

Starting with IBM® AIX® 7.2 with Technology Level 5, you can use the rpvutil command to perform the following operations:

Set the maximum expected delay before the application receives the I/O acknowledgments for a mirror pool in a volume group.
Compress the I/O data packet before it is sent from the RPV client to the RPV server or for monitoring the RPV network.
Monitor the RPV data network.
Change the cache size of the asynchronous I/O operations. You must increase the cache size by using the extendlv command before you run the rpvutil command.
Suspend and resume operations on the RPV server.
Enable or disable the cache full timer feature. However, if you disable the cache full timer feature, the buffered I/O operations are invalidated.
Set the cache full timer value.

The data in a remote site with GLVM configuration might become inconsistent in the following scenarios:

When the remote disk is not accessible during a write operation on the RPV server, but the remote disk is accessible during a site failover.
When a site failover occurs after the syncvg command fails on remote disk.
When the local site or the network fails during the execution of the syncvg command.

To handle these data inconsistency issues at the remote site, you can use the rpvutil command to perform the following tasks:

Suspend incoming I/O requests at the remote site.
Periodically save disk data snapshots on remote site’s storage disks or on cloud by using external utilities.
Resume I/O operations at the remote site.

During an unplanned site failover, if data in the remote site becomes inconsistent, restore snapshot data on remote disks by using external utilities.

Flags

-a: Displays the current values of all tunable parameters of the GLVM RPV client.
-c: Changes the cache size of the asynchronous I/O operations.
-d tunable_name: Resets the specified tunable parameter to its default value.
-h [tunable_name]: Displays help information for the rpvutil command. If you specify a tunable parameter with this flag, the command displays help information for the specified tunable parameter.

nw_sessions=number_of_sessions: Specifies the number of parallel RPV sessions (sender and receiver threads) per network. This tunable parameter is used to increase the number of parallel RPV sessions per GLVM network, which helps in sending the data in parallel and to improve the data transfer rate and use full bandwidth between the sites. A single RPV session on an RPV client consists of a sender thread for transfer of the data, and a receiver thread to receive the acknowledgment. Range of the nw_sessions is 1 - 99. You can change RPV value only when all the RPV devices on the AIX operating system are in defined state.
Note: When you change the number of sessions value to a higher value, you might create many threads. You must choose number of sessions value based on the workload.
cf_tmr_feature={1/0}: Enables or Disables the cache full timer feature. If this feature is enabled, the rpvutil command starts a timer when the I/O buffer cache is full. When the I/O buffer cache is full, all the subsequent I/O requests are buffered internally. When the timer expires, all the I/O requests that are buffered internally are invalidated and the threads of the application are released from the queue of threads that are waiting for the response from the I/O operations. Also, the physical volumes are moved to the stale state. You can set the timer value by using the cf_tmr_value tunable parameter.
cf_tmr_value=value_in_seconds: Sets the timeout value for the cache full timer feature. The timeout value can be in the range 2 - 30 seconds. The default timeout value is 10 seconds.

-o tunable_name[=value]

If you do not specify any value for the tunable parameter, the -o tunable_name flag displays the current values of the specified tunable parameter. You can specify the following tunable parameters for the rpvutil -o command:

compression=1|0

To use the compression tunable parameter, consider the following prerequisites:

Ensure that the RPV client and the RPV server are running AIX version 7.2.5, or later, with all the latest RPV device drivers.
Ensure that both the RPV server and the RPV client are IBM Power® Systems servers with NX842 acceleration units.
Ensure that the compression tunable parameter is enabled on both the RPV server and RPV client so that the I/O data packets are compressed when the workload is failed over between the RPV client and the RPV server.

When you set the compression tunable parameter to 1, the rpvutil command compresses the I/O data packet before it is sent from the RPV client to the RPV server by using the special acceleration units for cryptography and compression (NX842) that are available in IBM Power Systems servers. If the I/O data packet is compressed successfully, a flag is set in the data packet that is sent to indicate that the data packet is compressed. If the I/O data packet that is received at the RPV server has the compression flag enabled, the RPV server decompresses the I/O data packet. If the NX842 acceleration unit is not available in the RPV server, the RPV server attempts a software decompression operation instead of the hardware decompression operation. By default, this option is set to 0 (disabled).

io_grp_latency=timeout_value: Indicates the maximum expected delay, in milliseconds, before receiving the I/O acknowledgment for a mirror pool that is configured in asynchronous mode. You must specify the volume group that is associated to the mirror pool by using the -v flag. The default delay value is 10 ms. You can specify lesser values to improve I/O performance but CPU consumption might increase.

-r rpvs_name

Resume I/O operations on the volume group to which the rpverver device belongs.

-s rpvs_name

Suspend I/O operations on the volume group to which the rpverver device belongs.

-v vg_name

Specifies the name of the volume group name for which the tunable parameters are added, modified, or displayed.

Examples

To set a timeout value of 5 ms for the gmvg1 volume group, enter the following command:
```
rpvutil -v gmvg1 -o io_grp_latency=5
```
An output that is similar to the following example is displayed:
```
RPVC timeout: 10. ODM Value: 10
Updated timeout[5] to ODM VG: gmvg1
Updated timeout[5] to rpvc. VG: gmvg1
```
To check the value of the compression option, enter the following command:
```
rpvutil -o compression
```
An output that is similar to the following example is displayed:
```
compression[odm,driver]=ENABLED,ENABLED
```
To compress the I/O data packets before the I/O data packets are sent from the RPV client to the RPV server, enter the following command:
```
rpvutil -o compression=1
```
The command returns 0 after successful completion.
To set the network sessions, enter the following command:
```
rpvutil -o nw_sessions=2
```
An output that is similar to the following example is displayed:
```
Setting nw_sessions to 2
```
To display the current value of tunable parameter, nw_sessions, enter the following command:
```
rpvutil -o nw_sessions
```
An output that is similar to the following example is displayed:
```
nw_sessions = 1
```
To apply cache size of the asynchronous I/O operation on a volume group, enter the following command:
```
rpvutil -c -v vg_name
```
To suspend I/O operations on a volume group that contains the rpverver0 device, enter the following command:
```
rpvutil -s rpvserver0
```
To resume I/O operations on a volume group that contains the rpverver0 device, enter the following command:
```
rpvutil -r rpvserver0
```
To enable the cache full timer feature, enter the following command:
```
rpvutil -v agmvg -o cf_tmr_feature=1
```
To set the cache full timer value to 20 seconds, enter the following command:
```
rpvutil -v agmvg -o cf_tmr_value=20
```

Files

The /usr/lib/methods directory contains the rpvutil command.