Deployment Guide

Host I/O
When troubleshooting disk drive and connectivity faults, stop I/O to the affected disk groups from all hosts as a data protection
precaution.
As an extra data protection precaution, it is helpful to conduct regularly scheduled backups of your data. See “Stopping I/O” in
the Dell EMC PowerVault ME4 Series Storage System Owner’s Manual.
Dealing with hardware faults
Make sure that you have a replacement module of the same type before removing any faulty module. See “Module removal and
replacement” in the Dell EMC PowerVault ME4 Series Storage System Owner’s Manual.
NOTE: If the enclosure system is powered up and you remove any module, replace it immediately. If the system is used with
any modules missing for more than a few seconds, the enclosures can overheat, causing power failure and potential data
loss. Such action can invalidate the product warranty.
NOTE: Observe applicable/conventional ESD precautions when handling modules and components, as described in
Electrical safety on page 8. Avoid contact with midplane components, module connectors, leads, pins, and exposed circuitry.
Isolating a host-side connection fault
During normal operation, when a controller module host port is connected to a data host, the port host link status/link activity
LED is green. If there is I/O activity, the host activity LED blinks green. If data hosts are having trouble accessing the storage
system, but you cannot locate a specific fault or access the event logs, use the following procedures. These procedures require
scheduled downtime.
NOTE:
Do not perform more than one step at a time. Changing more than one variable at a time can complicate the
troubleshooting process.
Host-side connection troubleshooting featuring CNC ports
The following procedure applies to controller enclosures with small form factor pluggable (SFP+) transceiver connectors in 8/16
Gb/s FC or 10 GbE iSCSI host interface ports.
In this procedure, SFP+ transceiver and host cable is used to refer to any qualified SFP+ transceiver supporting CNC
ports used for I/O or replication.
NOTE:
When experiencing difficulty diagnosing performance problems, consider swapping out one SFP+ transceiver at a
time to see if performance improves.
1. Stop all I/O to the storage system. See “Stopping I/O” in the Dell EMC PowerVault ME4 Series Storage System Owner’s
Manual.
2. Check the host link status/link activity LED.
If there is activity, stop all applications that access the storage system.
3. Check the Cache Status LED to verify that the controller cached data is flushed to the disk drives.
● Solid – Cache contains data yet to be written to the disk.
● Blinking – Cache data is being written to CompactFlash in the controller module.
● Flashing at 1/10 second on and 9/10 second off – Cache is being refreshed by the supercapacitor.
● Off – Cache is clean (no unwritten data).
4. Remove the SFP+ transceiver and host cable and inspect for damage.
5. Reseat the SFP+ transceiver and host cable.
Is the host link status/link activity LED on?
● Yes – Monitor the status to ensure that there is no intermittent error present. If the fault occurs again, clean the
connections to ensure that a dirty connector is not interfering with the data path.
● No – Proceed to the next step.
6. Move the SFP+ transceiver and host cable to a port with a known good link status.
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Troubleshooting and problem solving