HP Storage Mirroring V5.1 Software - Manual (Page 75)

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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.

Exchange Server data is typically highly compressable, so it is recommended that compression
be enabled at level 2 on Exchange Server solutions.

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.
NOTE: Any replication sets from a source connected to the same IP address on a target will share
the same compression configuration.