When multiple containers are being replicated between the same DR appliances, the replication engine round-robins the
requests across the containers. In this situation the containers may not be replicated in synchronicity if there are large
amounts of data waiting to be transferred.
5.5
Replication Encryption
For best performance vs. security, encryption settings should be set at 128 bit encryption, providing a good balance for
most environments. For situations where the replicated data is being transferred across the open Internet, it is strongly
recommended to tunnel the replication traffic through an encrypted VPN tunnel.
5.6
Addressing Packet Loss
Occasionally a given link between two sites may introduce packet loss, resulting in slow data transfer or replication
processes that terminate due to errors or a simple timeout. When packet loss arises due to slow links, higher speed links,
jitter or high latency, the window size may need to be adjusted to account for this. In such instances please contact the
Dell Support department, and they will assist in custom tuning the window size for the particular link.
5.7
Replication Tuning
In some instances it may be beneficial to prevent replication from running all the time. Consider the following scenarios
when deciding whether to replicate on a per-container basis.
5.7.1
High Bandwidth Conditions
In situations where bandwidth is very high between a source and destination DR appliance, or many sources are
replicating to a single target appliance, the backup window may be negatively impacted when backups occur during the
replication process. If the backup window is unacceptable in such a scenario, the replication should be rescheduled to
occur outside the backup window, or the available bandwidth should be limited to < 50MB/s.
A high bandwidth scenario is when the WAN Bandwidth or Bandwidth between the source and destination DR units is >
100MB/s (800Mbits).
5.7.2
Reducing Bandwidth Concerns
A successful replication configuration interacts with its environment positively. In situations where replication traffic is
negatively impacting other services, fine tuning becomes necessary to limit the impact. The following suggestions will
help make sure replication is not placing a burden on other services.
1.
Make certain to schedule the replication process outside the hours where it could impact business. If video
conferencing or other business critical applications are experiencing the effect of a low-bandwidth situation,
verify the replication schedule and make sure it happens during non-business hours. Also, make sure to account
for the backup window when the daily backups are being stored to the DR appliance.
2.
In situations where the bandwidth of the impacted services is well known, the bandwidth available to the
replication process can be reduced. Throttling the replication bandwidth requires more time for the replication
process to complete, but leaves room for the impacted services to do their thing. For example, if video
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DR4100 Best Practice Guide | April 2014
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