Compression and Performance

Question

How does the Disk Safe compression influence CDP performance? 

Solution

The Disk Safe is smart enough to try and fit a compressed block into as small a space as possible. Compressing the Disk Safe data adds to overhead for reads and writes to the Disk Save. Using compression makes the Disk Safe work harder as the blocks are no longer fixed size, but average from 26 bytes to 4096 bytes.

Compression is done on the Agent, so it is compressed before it is written to the network. The compressed Disk sectors are sent over the network and stored in compressed form in the Disk Safe. Using a higher level of compression will increase CPU usage greatly on the computer where the agent is installed, with only marginal compression savings.

Restores will be slower when compression is used.

For Backups over the Internet or other slow links we recommend turning compression on. Using compression will help as we will have to send less data because compression is done before the data is transmitted. We recommend "No Compression" to complete Backups in the shortest amount of time over fast LANs (Local Area Networks).

See also: Disk Safe Compression (CDP Server 2.0 Documentation).

Selecting Level 1

Basically, level 1 is fastest. zlib delivers adequate compression levels on a wide variety of data with low CPU usage when you select level 1. We recommend level 1 unless you have CPU cycles to burn on the Agent side. In most cases, level 1 is a suitable selection.

Use of the first level gives you very good compression for minimal performance trade off, higher levels only give very small amounts of extra compression while suffering larger amounts of performance loss.

Selecting Level 3

If you're using compression, we usually recommend keeping the compression level at around 3 or below. Anything higher starts to add a lot more processing overhead for very little savings in space.

Selecting Level 6

For some users, level 6 can be a good compromise between speed and space.

Selecting Level 9

Level 9 reduces size the most but with a great increase in CPU usage. High compression levels can increase load where your agent is installed.

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