Expansion Enclosure - Loss of Path Redundancy

What Caused the Problem?

An enclosure with redundant physical disk loops (channels) has lost communication through one of its loops. The enclosure has only one loop available for I/O. The Recovery Guru Details area provides specific information you will need as you follow the recovery steps.

Loss of path redundancy can result from any of the following:

An SFP is inserted into one of the ports on an EMM module with a data rate that is not compatible with the data rate switch setting on the expansion enclosure.

Faulty EMM module (a separate problem should be reported)

Faulty SFP (a separate problem should be reported)

Removed RAID controller module module on an enclosure containing both RAID controller modules and physical disks

Disconnected or faulty physical disk cable

Improperly seated EMM module

An EMM module that supports selectable loop data rates is set to a rate that is not compatible with other devices on the loop.

Caution: Electrostatic discharge can damage sensitive components. Use a grounding wrist strap or other anti-static precautions before removing or handling components.

Important Notes

Correct this failure as soon as possible. Although the storage array is still operational, a level of path redundancy has been lost. If the remaining physical disk loop fails, all I/O to that enclosure will fail.

The Recovery Guru will report separate problems for any enclosures it cannot reach through the loop (channel) of the affected enclosure.

The Recovery Guru Details area reports the affected enclosure and the working channel over which it can communicate with the enclosure.

The amber bypass LED on the In or Out port of the EMM will glow if the associated port is not active in the physical disk loop.

The amber bypass LED on the In or Out port of the EMM will flash if the data rate of the SFP in the associated port is not compatible with the data rate switch setting on the expansion enclosure (for example, a 2 Gb/s SFP is installed in an enclosure that is set to 4 Gb/s).

The green power light on the EMM module will be off if the module is not seated properly.

The Event Log may also report an Extended fibre channel link down (greater than one minute) event (event 1019) in reference to this problem. Be sure to note the presence of this event when speaking with a technical support representative.

Recovery Steps

Fix any other problems reported by the Recovery Guru before attempting to fix this problem.

Look on the back of the expansion enclosures and see if any of the amber by-pass LEDs are flashing on the In or Out port of the EMMs (note that this behavior is not available on all models of expansion enclosures).

If...	Then...
An amber by-pass LED is flashing	The supported data rate of the SFP associated with the port is not compatible with the data rate switch setting on the expansion enclosure (for example, a 2 Gb/s SFP is installed in an enclosure that is set to 4 Gb/s). Remove the SFP and replace it with one that is compatible with the data rate switch setting on the expansion enclosure. Go to step 9.
An amber by-pass LED is NOT flashing	Either the expansion enclosure model doesn't support this LED flashing indication or all SFPs are compatible with the data rate setting on the expansion enclosure. Go to step 3.

If...

Then...

The RAID controller modules for this storage array are located in an enclosure containing both RAID controller modules and physical disks

If...

Then...

One of the RAID controller module modules is removed

Reinsert the RAID controller module.

Go to step 9.

Both RAID controller module modules are present

To locate the non-working channel, start with the RAID controller module module that is associated with the working channel. Looking at the RAID controller module modules from the back of the enclosure, RAID Controller Module A is the left RAID controller module module and is associated with channel 1. RAID Controller Module B is the right RAID controller module module and is associated with channel 2.

Go to step 4.

The RAID controller modules for this storage array are located in an enclosure containing only RAID controller modules

To locate the non-working channel, start with the physical disk port in the RAID controller module enclosure that corresponds to the working channel (refer to the labels on the back of the RAID controller module enclosure if needed).

Go to step 4.

Trace the cable from the working channel to the EMM module in the affected expansion enclosure reported in the Recovery Guru Details area.

Caution: Do not disconnect any cables on the working channel. Doing so will cause data loss!

Blink the other EMM module in the affected expansion enclosure and trace the cables back to the port on a RAID controller module enclosure or the RAID controller module module for the combination RAID enclosure. This is the non-working channel. When tracing the cables on the non-working channel, perform the following:

Check for loose or damaged cables. An amber loop bypass LED (In Bypass or Out Bypass) on the EMM will be lit if there is a connection problem between two enclosures.

Check for a loop data rate mismatch.

If...	Then...
The RAID controller modules for this storage array are located in an enclosure containing both RAID controller modules and physical disks	Look at the EMM modules on the non-working channel. If any of the EMM modules have a switch to set the loop data rate, use the Storage Array >> View >> Profile option and select the Enclosure tab to verify they are all set to the maximum data rate (for example, 1 Gb/s or 2 Gb/s).
The RAID controller modules for this storage array are located in an enclosure containing only RAID controller modules	If the EMM modules or physical disk channel port on the non-working channel has a switch to set the loop data rate, verify that they all are set to the same data rate (for example, 1 Gb/s or 2 Gb/s). Note that if the physical disk channel port or one of the EMM modules on the loop does not have a switch to set the loop speed setting switch, all of the other data rate switches on the physical disk channel loop must be set to 1 Gb/s.

If...	Then...
There is a connection problem or a loop data rate mismatch	Correct it and go to step 6.
There is not a connection problem or loop data rate mismatch	Go to step 6.

Click the Recheck button to rerun the Recovery Guru to ensure that the problem has been fixed.

If...	Then...
The problem does not appear in the Summary area	You are finished with this procedure.
The problem continues to appear in the Summary area	Go to step 7.

Check the green power light on each EMM module along the non-working channel. If it is off, then reseating the EMM module on the non-working channel may clear the failure being reported.

Reseat the module by removing it from the expansion enclosure and then wait 10 seconds. Re-insert the module firmly, wait another 40 seconds, then go to step 8.

Click the Recheck button to rerun the Recovery Guru. The failure should no longer appear in the Summary area. If the failure appears again, contact your technical support representative.