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Document ID:4471
Subject:Modifying rsync's block size in Syncrify
Creation date:11/4/15 9:27 AM
Last modified on:12/12/18 3:16 PM

Modifying block size for Rsync

As required by the Rsync algorithm, Syncrify breaks every file into multiple blocks and checksum are matched for every block when computing the delta. By default, Syncrify creates up to 131,072 blocks for a file. This means for a file that is 20GB in length, every block will be approximately 1.6 MB. This means even if one byte changes in the file, the delta will not be smaller than 1.6MB.

Block matching is done on the client machine and therefore, if most of your client machines are servers, this means faster CPU and more memory. Thus, you can increase the number of blocks, which will reduce the block size and could potentially decrease the size of the delta file.

Note that a higher number of blocks means more time will be spent in matching blocks but will result in a smaller delta. In other words, it is more work for the CPU but less for the network.

How to change this setting?

This parameter cannot be set from the server's web interface. You have to set it manually by using the following method:
  • Locate AppConfig.xml file in $INSTALL_DIR\config folder.
  • Add (modify if already exists) the following parameter.

    <parameter name="MaxRsyncBlockSize" type="1" value="131072"></parameter>

  • Change the value of this parameter to the desired number.
  • Save the file and restart Syncrify

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