20.11.7.2 Using Relinker in the Command Line Mode

relinker scans through a message store partition, creates or updates the MD5 message repository (as hard links) and deletes excess message files. After relinker scans a store partition, it outputs statistics on the number of unique messages and size of the partition before and after relinking. To run more quickly on an already hashed store, relinker only computes the digest of the messages not yet present in =md5. It also has an option to erase the entire digest repository (which doesn’t affect the user mailboxes).

The syntax for the command is as follows:

relinker [-P. partitionname] [-d]

where partitionname specifies the partition to be processed (default: all partitions) and -d specifies that the digest repository be deleted. Sample output is shown below:

# relinker

Processing partition: primary
Scanning digest repository...
Processing user directories..............................
---------------------------------------------------------
Partition statistics           Before            After 
---------------------------------------------------------
Total messages                 4531898         4531898
Unique messages                4327531         3847029
Message digests in repository        0         3847029
Space used                       99210Mb         90481Mb
Space savings from single-copy    3911Mb         12640Mb
---------------------------------------------------------


# relinker -d 
Processing partition: primary
Purging digest repository...
---------------------------------------------------------
Partition statistics                 Before         After
---------------------------------------------------------
Message digests in repository       3847029             0
---------------------------------------------------------

Relinker can take a long time to run, especially for the first time if there are no messages are in the repository. This is because it has to calculate the digest for every message (if the relinker criteria is configured to include all messages—see 20.11.7.4 Configuring Relinker for information on configuring relinker criteria.) For example, it could take six hours to process a 100 Gigabyte message store. However, if run-time relinking is enabled see 20.11.7.3 Using Relinker in the Realtime Mode.

If the relinker command line mode is used exclusively, and not the run-time option, it is necessary to purge the digest repository (=md5), otherwise messages purged in the store (=user) will not become available disk space since they still have a link in the digest repository (they become orphaned). If you are just performing a one-time optimization of the store—for example after a migration—you can run relinker once, then delete the entire repository with relinker -d. For repeated purging during migration, it is sufficient to just run the relinker command repeatedly, since each time it runs it also purges the expired or orphaned messages from the repository.

It is safe to run multiple instances of relinker in parallel with each processing a different partition (using the -p option). Messages are only relinked inside the same partition.