Dell PowerVault MD3000 - Manual (Page 99)

Maintaining a Storage Array
99
Diagnosing a RAID Controller Module
The diagnose controller command’s testID parameter takes the following
options, which you can use to verify that a RAID controller module is
functioning correctly:
• 1— Reads the test
• 2— Performs a data loop-back test
• 3— Writes the test
The read test initiates a read command as it would be sent over an I/O data
path. The read test compares data with a known, specific data pattern,
checking for data integrity and errors. If the read command is unsuccessful or
the data compared is not correct, the RAID controller module is considered to
be in error and is placed offline.
Run the data loopback test only on RAID controller modules that have
connections between the RAID controller module and the physical disks. The
test passes data through each RAID controller module physical disk-side
channel out onto the loop and back again. Enough data is transferred to
determine error conditions on the channel. If the test fails on any channel,
this status is saved so that it can be returned if all other tests pass.
The write test initiates a write command as it would be sent over an I/O data
path to the diagnostics region on a specified physical disk. This diagnostics
region is then read and compared to a specific data pattern. If the write fails
or the data compared is not correct, the RAID controller module is considered
to be in error, and it is failed and placed offline.
For best results, run all three tests at initial installation. Also, run the tests any
time you make changes to the storage array or to components connected to
the storage array (such as hubs, switches, and host adapters).
A custom data pattern file called diagnosticsDataPattern.dpf is included on
the Utility directory of the installation CD. You can modify this file, but the
file must have the following properties to work correctly for the tests:
• The file values must be entered in hexadecimal format (00 to FF) with
only one space between the values.
• The file must be no larger than 64 bytes in size. Smaller files can be used,
but larger files can cause an error.