Impact of bandwidth constraints
File/registry replication is impacted by bandwidth between replicated nodes in the sense that the time required to transmit changes from one node to another will be at least the size of the change divided by the bandwidth available. For example, if a 100MByte executable is installed on the primary node and 10Mbps is available between application nodes, then the time to transmit the change will be at least:
T = (100 * 10 6 * 10bits/byte)=(10 * 10 6 ) = 100sec
In practice, latency adds further delay to this calculation, as described in Impact of network latency , so in the best case scenario using the data above, the actual time would be more than 100sec.
Similarly, database replication is impacted by bandwidth by limiting the rate at which stored procedure calls can be forwarded from one node to another. Since stored procedures arrive at each application node sporadically, they are more impacted by latency, which adds a "fixed cost" to each batch of stored procedures. In practice, it is only transfers of relatively large data sets – for example during auto-discovery, that are noticeably impacted by bandwidth.
Best practice
Bravura Security recommends placing Bravura Security Fabric database nodes at locations with at least 5Mbps bandwidth available between them.
In practice, low network bandwidth, where application nodes have less than 1Mbps of bandwidth available to propagate changes from one to another, has the following impacts:
The time required to complete file/registry replication during nightly auto-discovery will grow – with the delay being determined by (a) the volume of data that needs to be forwarded and (b) the available bandwidth.
The time required to complete database replication for large volumes of data – that is, during nightly auto discovery and under heavy load conditions – can grow. In some cases (that is, high load (for example, Gigabyte volumes), very low bandwidth (for example, 100kbps)) a substantial backlog can develop.
Estimating bandwidth requirements
Nightly auto-discovery
The bulk of data transmission between application nodes during the nightly auto-discovery process is to transfer list files from the primary application node, where they are generated, to all other nodes. Since compression is used, on average, the total data transmitted will generally be less than half of the disk space consumed on the primary node by these files.
For example, if lists of users, groups, account attributes and computer groups on the primary node consume 50MB of disk space then no more than 25MB of network bandwidth will be used during nightly auto-discovery to transfer this data set to each secondary application node.
Real time database replication
The volume of data replication between servers depends on the workload generated by each server. Some rough rules of thumb are:
With Bravura Pass , every user login session, either to change passwords or enroll security questions, will generate about 29 replicating procedures.
With Bravura Identity , every workflow request (input, approvals, fulfillment) will generate about 200 replicating procedures.
With Bravura Privilege , every scheduled password randomization will generate about 20 replicating procedures.