Cache Memory And Cache Battery; Cache Memory - IBM DS3500 Installation, User & Maintenance Manual

10. Diagnose and correct the fault.
11. Replace the bezel on the expansion enclosure, if applicable.

Cache memory and cache battery

Each RAID controller in the DS3500 storage subsystem contains 1 GB or 2 GB of
cache memory to store read and write operations. In a dual RAID controller
configuration, both controllers in the DS3500 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 DS3500 power failure.

Cache memory

Cache memory is memory on the RAID controller that is used for intermediate
storage of read and write data on the DS3500 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.
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System Storage DS3500 and EXP3500: Installation, User's, and Maintenance Guide
6. Turn off both power switches on the DS3500 (see Figure 66 on page 69) and
then power-off all connected expansion enclosures. Wait 1 minute and then
turn on power to all connected expansion enclosures.
While an expansion enclosure powers-on, the LEDs on the front and the rear
of the enclosure flash intermittently. Depending on your configuration, the
expansion enclosure can take between 20 seconds and several minutes to
power-on.
7. Turn on both power switches on the rear of the storage subsystem. See
Figure 66 on page 69.
A storage subsystem can take 10 seconds to power-on and up to 15 minutes
for the battery self-test to be completed. During this time, the LEDs on the
front and the rear of the DS3500 flash intermittently.
8. Check the LEDs on the front and rear of the storage subsystem and each
attached expansion enclosure (a green LED indicates a normal status; an
amber LED indicates a hardware fault); then, check the array status in the
Subsystem Management window.
a. Open the Subsystem Management window for the storage array.
b. Click the Summary tab and review the status of the configuration.
The status is either Optimal or Needs Attention.
9. Does each module (RAID controller, power supply, ESM) display green status
LEDs only, and is the status Optimal for each module component?
v Yes: Go to step 11.
v No: Go to step 10.
a. To run the Recovery Guru, click Recovery Guru in the toolbar 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 73.
c. When the procedure is completed, select Recheck in the Recovery Guru.
This runs the Recovery Guru again to make sure that the problem is
corrected.
d. If the problem remains, contact your IBM technical-support representative.