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19 PS Series Asynchronous Replication Best Practices and Sizing Guide | BP1012
volume behaves as if it were a standard volume and the contents of the entire volume will be copied during
initial replication.
6.4 Theoretical bandwidth of links and replication time
Because the TCP/IP protocol carries some overhead, the speed of the network alone provides insufficient
information to estimate the time it will take for replication. In a typical SAN environment, Dell EMC
recommends using Jumbo Frames (9000 bytes) to get maximum performance. However, because most WAN
routers or other long-distance connectivity does not support Jumbo Frames, we would typically consider the
standard MTU of 1500 bytes in our calculations. Use the following calculations to calculate an estimate for
maximum link throughput:
Maximum throughput (MB/sec) = [WAN link speed (Mb/sec)/8 bits per byte] x 93% protocol efficiency
Use the estimate for throughput to estimate replication time for a given amount of data:
Replication time = volume size (MB) / throughput
Considering an OC3 link, which is rated at 155 Mbps, use the following:
Maximum throughput in MB/sec = 18.02 MB/sec
Time to transmit 100GB volume = 102400 / 18.02 = 5683 sec (~95 minutes)
This result closely correlates with the actual time measured in the lab test, as shown for the OC3 (155Mb/sec)
link speed in Figure 8. These sample calculations assume that all of the link bandwidth is available.