10. Check the status LEDs on the front and back of the storage subsystem.
a. Note the status of the LEDs on the front and back of each module.
A green LED indicates a normal status; amber LEDs indicate a hardware
fault.
b. Open the Subsystem Management window for the storage array.
c. Select the applicable components button for each module in the Physical
View of the Subsystem Management window to view the status of its
components.
The status for each component is either Optimal or Needs Attention.
11. Does each module display green LEDs only,and is the status Optimal for each
module component?
vYes - Go to step 13.
vNo - Go to step 12.
12. Diagnose and correct the fault.
a. Torun the Recovery Guru, select the Recovery Guru toolbar button in the
Subsystem Management window.
b. Complete the recovery procedure.
If the Recovery Guru directs you to replace a failed component, locate and
troubleshoot that component. See “Checking the LEDs” on page 101.
c. When the procedure is completed, rerun the Recovery Guru to make sure
that the problem has been corrected by selecting Recheck in the Recovery
Guru.
d. If the problem persists, contact IBM Customer and TechnicalSupport.
13. Replace the bezel on the storage expansion enclosure, if applicable.
Cache memory and cache battery
Each RAID controller in the DS5020 storage subsystem contains either 1 GB or 2
GB of cache memory to store read and write operations. (Both RAID controllers in
the DS5020 must have the same amount of cache memory.)The battery unit
contains enough charge to back up the cached data in each controller to a flash
drive in the event of a DS5020 power failure.
Attention: There are different replacement FRU part numbers for the DS5020
controller with certain cache sizes. The DS5020 storage subsystem profile has the
information about the installed cache memory size in the DS5020 controllers. Refer
to the storage subsystem profile and see “Parts listing” on page 160 for the correct
FRU part number for the DS5020 controller.
Cache memory
Cache memory is memory on the RAID controller that is used for intermediate
storage of read and write data on the DS5020 RAID controllers. Using cache
memory can increase system performance. The data for a read operation from the
host might be in the cache memory from a previous operation (thus eliminating the
need to access the drive itself), and a write operation is completed when it is written
to the cache, rather than to the drives.
The RAID controller has a Cache Active LED that displays the current status of the
cache. The LED is on if there is data in the cache, and it is off if there is no data in
the cache.
116 IBM System Storage DS5020 Storage Subsystem: Installation, User ’s, and Maintenance Guide