HP StorageWorks Storage Mirroring for Linux User's Guide (T2558-96317, June 2009)

9 - 13
Configuring compression
To help reduce the amount of bandwidth needed to transmit Storage Mirroring data, compression
allows you to compress data prior to transmitting it across the network. In a WAN environment this
provides optimal use of your network resources. If compression is enabled, the data is compressed
before it is transmitted from the source. When the target receives the compressed data, it
uncompresses it and then writes it to disk. On a default Storage Mirroring installation, compression
is disabled.
Keep in mind that the process of compressing data impacts processor usage on the source. If you
notice an impact on performance while compression is enabled in your environment, either adjust to
a lower level of compression, or leave compression disabled. Use the following guidelines to
determine whether you should enable compression:
 If data is being queued on the source at any time, consider enabling compression.
 If the server CPU utilization is averaging over 85%, be cautious about enabling compression.
 The higher the level of compression, the higher the CPU utilization will be.
 Do not enable compression if most of the data is inherently compressed. Many image (.jpg,
.gif) and media (.wmv, .mp3, .mpg) files, for example, are already compressed. Some images
files, such as
.bmp and .tif, are uncompressed, so enabling compression would be beneficial
for those types.
 Compression may improve performance even in high-bandwidth environments.
 Do not enable compression in conjunction with a WAN Accelerator. Use one or the other to
compress Storage Mirroring data.
1. Right-click the connection on the right pane of the Management Console and select Connection
Manager.
2. Select the Compression tab.
3. By default, compression is disabled. To enable it, select Enable Compression.
4. Depending on the compression algorithms available for your operating system, you may see a
slider bar indicating different compression levels. Set the level from minimum to maximum
compression to suit your needs.
5. Click OK to save the settings.
Disconnecting a connection
To disconnect a Storage Mirroring connection, right-click the connection on the right pane of the
Management Console and select Disconnect. The source and target will be disconnected.
NOTE: Any replication sets from a source connected to the same IP address on a target will share
the same compression configuration.
NOTE: If a connection is disconnected and the target is monitoring the source for failover, you
will be prompted if you would like to continue monitoring for a failure. If you select Yes,
the Storage Mirroring connection will be disconnected, but the target will continue
monitoring the source. To make modifications to the failure monitoring, you will need to
use the Failover Control Center. If you select No, the Storage Mirroring connection will
be disconnected, and the source will no longer be monitored for failure by the target.
If a connection is disconnected while large amounts of data still remain in queue, the
Management Console may become unresponsive while the data is being flushed. The
Management Console will respond when all of the data has been flushed from the queue.