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c:\>fsradm invalidate r0 |
Automatic synchronization
Except for manual manipulation, synchronization is all automatic by default once a mirroring connection is established. FSR does not track changes between files or keep information about them in advance for file synchronization (this is not practical in the realm of file replication). It identifies and synchronizes differences between files on the fly at the time the synchronization is performed.
How file differences are compared
Sync has several customizable behaviors, depending on how aware it is of differences between files on both sides. The behavior makes a difference in how fast the sync performs, so be sure to configure it to a reasonable value.
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The values you specify for comparison_level have the following meanings
- 0: Full sync, no comparison. It synchronizes the entire file unconditionally, so it takes longer, but it provides the best guarantee of matching.
- 1: Attribute comparison sync, compares the differences in the attributes of the files and synchronizes them. This is the preferred method because it synchronizes quickly.
- 2: Hash comparison sync, get the hash values of the files, compare them, and sync if there are differences. The hash algorithm can be specified by choosing from CRC32, MD5, SHA1, SHA256, or SHA512 as the HASH_TYPE value.
However, hash comparison synchronization may take precedence over attribute comparison synchronization (1) in the following situations. When replicating DB files, hash comparison synchronization should be specified as the default.
However, hash comparison synchronization may take precedence over attribute comparison synchronization (1) in the following situations.
- When the target's file is unlocked
- When the source side fails or is forced to reboot (crashed primary) due to an operational failure.
In unintended operational and failure-like situations, comparison via file attribute values may not always be consistent, so hash comparison synchronization is used to ensure consistency between files.
Replications
As the secondary node is promoted and synchronization starts, if a real-time change occurs in the data of the source node, the change is automatically reflected in parallel. Replication is defined as an action that reflects real-time changes in local data to a target in real time, and proceeds from the primary node to the secondary node.
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