Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 128)

Chapter 7. Configuring Units
116 3ware SATA+SAS RAID Controller Card Software User Guide, Version 10.2
This section includes the following topics about changing existing
configurations:
• RAID Level Migration (RLM) Overview
• Changing RAID Level
• Expanding Unit Capacity
• Informing the Operating System of Changed Configuration
If you want to change the policy settings for an existing unit, there is no need
to change the configuration. See “Setting Unit Policies” on page 100.
RAID Level Migration (RLM) Overview
RAID level migration is the process of converting one RAID configuration to
another. When you migrate a unit to a different configuration, the user data on
it is redistributed to the format of the new configuration. This data
redistribution process is a background task, similar to the rebuild or verify
processes.
Figure 62 shows an example of how data is reconfigured during a migration.
In this example, the migration is from a 3-drive RAID 0 to a 4-drive RAID 5,
with both having the same stripe size. As can be seen, every piece of user data
is moved from its original physical location.
Figure 62. RAID Level Migration Example
Typically, a unit is reconfigured with the same or more storage capacity.
Sometimes additional drives are added. The following table shows valid
reconfigurations, some of which will require the addition of more drives.