You have to replace a Cache Backup Battery online on a Hitachi Unified Storage system. Which two statements are correct? (Choose two.)

Question

Options

• AWhen the power is turned off during the replacement, user data on the cache that has not been
• BYou should not perform any replacement while the green READY LED on the front of the Controller
• CYou should only perform the replacement while the green READY LED on the front of the
• DYou must complete the replacement within a certain time frame.

Explanation

Based on Hitachi Unified Storage documentation for online Cache Backup Battery (CBB) replacement, the correct answers are C and D.

Why C is correct: The green READY LED being illuminated confirms the controller is in a normal, stable operating state - this is the required condition for safe online battery replacement. Performing the swap while the system is healthy ensures the controller can properly manage the cache during the brief unprotected window.

Why D is correct: During the replacement, the cache temporarily loses its battery backup protection. If a power failure occurred in this window, any unwritten cache data could be lost. To minimize this risk, Hitachi requires the replacement be completed within a defined time limit.

Why A is wrong (distractor): While it raises a real concern about data loss if power fails, performing the replacement correctly (per the procedure, with READY LED on) manages this risk - it doesn't describe a reason to avoid the procedure.

Why B is wrong (distractor): B is the direct opposite of C. Avoiding replacement when the READY LED is green would mean you can never safely do it online, which contradicts the purpose of an online replacement procedure.

Memory tip: Think "Green means Go, but Go Fast." The READY LED green = safe to start (C), and the timer pressure means don't dawdle (D). If the LED isn't green, the system isn't ready - just like a traffic light.

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