3.6 Given a scenario, install the appropriate power supply.
📘CompTIA A+ Core 1 (220-1201)
A redundant power supply is a setup where two or more power supplies are installed in a device (like a server) so that if one fails, the other can continue providing power without shutting down the device.
- The goal is high availability and reliability.
- Commonly used in servers, data centers, and enterprise-level networking equipment.
Think of it as a “backup inside the system” — it keeps the device running even if one power supply fails.
Key Points for the Exam
1. How Redundant Power Supplies Work
- Devices with RPS usually have two or more power supply units (PSUs).
- These power supplies are connected to separate power sources. This protects against:
- Failure of a PSU.
- Power source issues (like a faulty outlet).
- Power supplies can operate in two main modes:
- Active/Passive:
- One PSU is actively supplying power.
- The other is idle, only kicks in if the active one fails.
- Load Sharing / Active/Active:
- Both PSUs share the power load equally.
- If one fails, the remaining PSU(s) handle 100% of the power without downtime.
- Active/Passive:
2. Benefits of Redundant Power Supplies
- High Availability:
Devices remain powered even if one PSU fails. - Hot Swappable:
Many redundant PSUs are hot-swappable, meaning you can replace a failed PSU without shutting down the device. - Minimized Downtime:
Essential for servers and network devices that must run 24/7. - Improved Reliability:
Reduces the risk of unexpected failures affecting critical systems.
3. Typical Use Cases
- Servers: Enterprise servers often use redundant power supplies to avoid downtime for databases, websites, or applications.
- Networking Equipment: Core switches and routers in a network might have dual PSUs to prevent network interruptions.
- Storage Systems: SAN (Storage Area Networks) and NAS (Network Attached Storage) use RPS to ensure continuous access to data.
4. Redundant Power Supply Features
| Feature | Description |
|---|---|
| Hot-swappable | Can replace the PSU without shutting down the device. |
| Dual input | Each PSU can connect to different electrical circuits to avoid a single point of failure. |
| Status LEDs / Alerts | Indicate PSU health and failure. |
| Load balancing | Distributes power evenly to prevent overloading a single PSU. |
5. Exam Tip
For CompTIA A+ 220-1201, remember:
- Redundant power supplies prevent downtime.
- They are common in servers and enterprise devices.
- Hot-swappable capability is a key advantage.
- Can operate in Active/Passive or Load Sharing/Active-Active mode.
A simple way to remember:
“If one power supply dies, the other one keeps the system alive.”
✅ Summary for Students
- Purpose: Keep devices running without interruption.
- Where: Servers, networking gear, storage systems.
- Modes: Active/Passive or Load Sharing (Active/Active).
- Benefits: High availability, hot-swappable, reduces downtime.
- Exam Focus: Know the concept, benefits, and hot-swap capability.
