File Replication Set Test

A change order is a message that contains information about a file or folder that has changed on a replica.

These measures therefore serve as good indicators of the workload on the replica set.

Installation is the process by which FRS applies a change order to the local file system to restore the file or folder as it is in the upstream partner. If the change order is for a deletion, the file or folder in the local file system is deleted (staging file is not needed). If the change order is for a renaming, the file or folder in the local file system is renamed (staging file is needed). If the change order is for a copying or creation, the file or folder is copied or created (staging file is needed).

Installing a file or folder may fail if the file or folder is already opened by another process. If the installation failed, FRS retries installing the file or folder at a later time.

In an idle state, there should be no packets received unless a computer is having trouble joining with other computers in the replica set.

Active Directory replication does not primarily depend on time to determine what changes need to be propagated. Instead it uses update sequence numbers (USNs) that are assigned by a counter that is local to each domain controller. Because these USN counters are local, it is easy to ensure that they are reliable and never run backward (that is, they cannot decrease in value).

Domain controllers use USNs to simplify recovery after a failure. When a domain controller is restored following a failure, it queries its replication partners for changes with USNs greater than the USN of the last change it received from each partner.

The Staging Directory is an area where modified files are stored temporarily either before being propagated to other replication partners or after being received from other replication partners. FRS encapsulates the data and attributes associated with a replicated file or directory object in a staging file. FRS needs adequate disk space for the staging area on both upstream and downstream machines in order to replicate files.

Typically, if the Staging space free measure reports the value 0, or is found to be dangerously close to 0, it indicates that the staging directory is full. If the staging area is full, the FRS will stop functioning, and will resume only if disk space for the staging area becomes available or if the disk space limit for the staging area is increased.

The staging area could get filled up owing to the following reasons:

One or more downstream partners are not accepting changes. This could be a temporary condition due to the schedule being turned off and FRS waiting for it to open, or a permanent state because the service is turned off, or the downstream partner is in an error state.

The rate of change in files exceeds the rate at which FRS can process them.

A parent directory for files that have a large number of changes is failing to replicate, and so, all changes to subdirectories are blocked.