Specifications

Determine Network Bandwidth Requirements
sufficient bandwidth to successfully replicate the partition and keep the mirror in the mirroring state as
the source partition is updated throughout the day?"
Keeping the mirror in the mirroring state is critical because a switchover of the partition is not allowed
unless the mirror is in the mirroring state.
Determine Network Bandwidth Requirements
Prior to installing SteelEye DataKeeper, you should determine the network bandwidth requirements
for replicating your data. Use the method below to measure the rate of change for the data that you
plan to replicate. This value indicates the amount of network bandwidth that will be required to
replicate that data.
After determining the network bandwidth requirements, ensure that your network is configured to
perform optimally. If your network bandwidth requirements are above your current available network
capacity, you must consider one or more of the following options:
l Enable compression in DataKeeper, or in the network hardware, if possible
l Create a local, non-replicated storage repository for temporary data and swap files that don't
really need to be replicated
l Reduce the amount of data being replicated
l Increase your network capacity
SteelEye DataKeeper handles short bursts of write activity by adding that data to its async queue.
However, make sure that over any extended period of time, the disk write activity for all replicated
volumes combined remains, on average, below the amount of change that DataKeeper and your
network can transmit.
If the network capacity is not sufficient to keep up with the rate of change that occurs on your disks,
and the async queue fills up, the mirror will revert to synchronous behavior, which can negatively
affect performance of the source server.
Measuring Basic Rate of Change
Use the following command to determine file(s) or partition(s) to be mirrored. For example
/dev/sda3, and then measure the amount of data written in a day:
MB_START=`awk '/sda3 / {print $10 / 2 / 1024 }'
/proc/diskstats`
… wait for a day …
MB_END=`awk '/sda3 / {print $10 / 2 / 1024 }'
/proc/diskstats`
The daily rate of change, in MB, is then MB_END – MB_START.
268Installation and Configuration