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DR Series Best Practice Guide

fewer expansion shelves in order to provide the necessary resources for improved

performance.

Calculate Replication Interval

Calculating the required bandwidth for replication will assist in properly sizing the infrastructure for

maximum performance. In order to calculate the time required to replicate a given container the

following two points of data are required:

1. Identify the amount of data that will be replicated. A common method is to view current

backup jobs and log files to determine the amount of data being backed up each day. The

more precise this number is, the more accurate the bandwidth calculation will be.

Since any data transferred during replication has already been compressed and deduplicated

to roughly 85%-90% of the original size, start by multiplying the original data size by 15% to

determine the amount of data to be replicated. For example, to transfer two terabytes of data,

break it down into megabytes by multiplying the value by 1048576. To convert 2TB to MB the

formula would be: 2TB * 1048576 = 2097152 MB.

Now, reduce this number by 85% and assign it to the variable: replica_data:

replica_data = 2097152 MB * .15 = 314572 MB.

2. Determine the effective bandwidth. A common method to determine bandwidth between two

sites utilizes a freeware product called iPerf (https://code.google.com/p/iperf/). The following

steps provide the command line instructions to calculate bandwidth:

a. Run iperf –s –w 5M on a server at the central site.

b. Run iperf –c <IP of server at central site> -w 5M

c. Capture the resulting bandwidth reported from the server at the central site, showing

the calculated bandwidth between sites.

Assign the acquired bandwidth value to the variable effective_bandwidth. This value may be

obtained from other methods of your choosing, but should be specified in MB for further

calculations. A bandwidth value of 10MB will be used for the following example.

3. Determine the acceptable amount of time allowed for replication. Convert the allowed

replication time to seconds.(i.e. 10 hours converted is 10*60*60 = 36000 seconds)

With this information, the following formula can be used to calculate the time required to replicate the

data.

replication_interval = replica_data / effective_bandwidth

Using the example of 2TB and a 10MB effective bandwidth, time can be calculated as follows:

replication_interval = 314572 MB / 10 MB = 31457 seconds (8.7 hours)

Bandwidth Optimization

When utilizing replication, it may be necessary to enforce bandwidth limitations. This can lower the

impact of replication traffic on the network. For example, if the WAN link also is required to support