User`s guide

Drive Roaming
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COD plays a significant role during the power-on sequence after a controller is replaced.
The replacement controller tests the validity of any configuration currently present in its
NVRAM. Then, it test the validity of the COD information on all disk drives in the
storage system. The final configuration is determined by the following rules:
1. The controller will use the most recent COD information available, no matter where
it is stored. The most recent COD information is updated to all configured drives.
Unconfigured drives are not updated; all COD information on these drives is set to
zero.
2. If all of the COD information has an identical timestamp, the controller will use the
COD information stored in its NVRAM.
Caution: Any existing COD on a disk drive that is inserted after the controller has
started (STARTUP COMPLETE) will be overwritten.
Caution: Mixing controllers or disk drives from systems running different versions of
firmware presents special situations that may affect data integrity. If a new disk drive
containing configuration data is added to an existing system while power is off, the
controller may incorrectly adopt the configuration data from the new drive. This may
destroy the existing valid configuration and result in potential loss of data. Always add
drives with the power supplied to the system to avoid potential loss of data.
Drive Roaming
Drive roaming allows disk drives to be moved to other channel/target ID locations while
the system is powered down. Drive roaming allows for easier disassembly and assembly
of systems, and potential performance enhancement by optimizing channel usage.
Drive roaming uses the Configuration on Disk (COD) information stored on the physical
disk drive. When the system restarts, the controller generates a table that contains the
current location of each disk drive and the location of each drive when the system was
powered down. This table is used to remap the physical disk drives into their proper
location in the system drive. This feature is designed for use within one system
environment, for example, a single system or a cluster of systems sharing a simplex or
dual-active controller configuration. Foreign disk drives containing valid COD
information from other systems must not be introduced into a system. If the COD
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