Upgrading or replacing LRC, ESH, ESH2, or AT-FCX modules

About the modules

The LRC, ESH, ESH2, or AT-FCX module in a DS14, DS14mk2 FC, or DS14mk2 AT includes a SCSI-3 Enclosure Services Processor. It maintains the integrity of the loop when disks are swapped and provides signal retiming for enhanced loop stability. There are two modules in the middle of the rear of the disk shelf, one for Channel A and one for Channel B.

Note
The Input and Output ports on module B on the DS14/DS14mk2 FC are the reverse of module A.

Connectors in an LRC, ESH, ESH2, or AT-FCX

The module has the following connectors.

Module connector	Function
Input	Provides the interface between the disk shelf and the storage system.
Output	Provides the interface between two disk shelves to create a loop of daisy-chained disk shelves.

Restrictions for changing module types

If you plan to change the type of any module in your cluster, make sure you understand the following restrictions about module types:

You cannot mix LRC and ESH modules in the same loop. Doing so will result in loop failure.
To replace an ESH with an ESH2, you must
- be running Data ONTAP 6.4.4 or later
- replace all ESH modules in the same shelf with ESH2 modules

Best practices for changing modules

The following list describes important guidelines and requirements you should understand and practice when changing modules in your cluster.

Whenever you remove a module from a cluster, you need to know whether the path you will disrupt is redundant. If it is, you can remove the module without interfering with the storage system's ability to serve data. However, if that module provides the only path to any disk in your cluster, you must take action to ensure that you do not incur system downtime.
For more information, see Understanding single and dual pathing in clusters.
When you replace a module, make sure that the replacement module's termination switch is in the same position as the module it is replacing.
Note
ESH2 modules are self-terminating; this guideline does not apply to ESH2 modules.
If you replace a module with a different type of module, make sure that you also change the cables if necessary.
For more information about supported cable types, see the Hardware Guide for your disk shelf.
Always wait 30 seconds after inserting any module before reattaching any cables in that loop.

Testing the modules

To test your LRC, ESH, ESH2, or AT-FCX modules after you replace or upgrade them, complete the following steps on both nodes.

Step	Action
1	Verify that all disk shelves with LRC, ESH, ESH2, or AT-FCX modules are functioning properly by entering the following command: environ shelf Results The system reports the modules as good.
2	Verify that there are no missing disks by entering the following command: aggr status -r Result Local disks displayed on the local node should be displayed as partner disks on the partner node, and vice-versa.
3	Verify that you can create and retrieve files on both nodes for each licensed protocol.

Step

Action

Verify that all disk shelves with LRC, ESH, ESH2, or AT-FCX modules are functioning properly by entering the following command:

environ shelf

Results

The system reports the modules as good.

Verify that there are no missing disks by entering the following command:

aggr status -r

Result

Local disks displayed on the local node should be displayed as partner disks on the partner node, and vice-versa.

Verify that you can create and retrieve files on both nodes for each licensed protocol.

For detailed information

For details about upgrading or replacing LRC, ESH, ESH2, or AT-FCX modules, see the following topics: