Why does a NAS/server need a UPS (even with "stable" power)?

Why does a NAS/server need a UPS (even with "stable" power)?

A NAS (Synology/QNAP) or a mini-server doesn't only suffer from "long power outages." The real danger is:

  • short haircuts,

  • voltage drops,

  • cascading restarts,

  • and abrupt shutdowns during disk writing.

The purpose of the UPS here is to provide enough time for the NAS to properly shut down (shutdown/standby), protecting the file system and data.

1) What to connect to the UPS (for NAS) and what to avoid

Connect to the UPS (priority):

  • IN THE

  • Router/switch (if you need the NAS to notify other devices on the network)

  • (Optional) 1 AP/mesh to keep the network up during the process.

Avoid using the same UPS (if you want autonomy):

  • Gaming PCs, heaters, large and variable loads (which consume battery power).

2) Sizing: watts first, then VA

Use the VA/W ratio correctly to avoid undersizing:

  • Watts = VA × Power Factor

And it maintains a margin. Eaton recommends choosing capacity with extra capacity (e.g., at least ~15% above what's needed), especially for growth and peak demand.

Quick example:

  • NAS: 60–120 W (depends on disks/CPU)

  • Switch: 10–30 W

  • Router/ONT: 20–35 W
    Typical total: 120–185 W

  • 20–30% margin → 150–240 W (as a comfort target)

3) The "key point": automatic shutdown (without it, it's practically an uninterruptible power supply - UPS).

For NAS/server, the "gold standard" is a UPS with communication capability .

  • USB (simpler)

  • SNMP (professional, ideal for racks and multiple devices)

Schneider/APC itself highlights features such as connectivity and expansion via network/management cards on certain product lines.

4) Synology: How to configure a UPS via USB and SNMP (the essentials)

Synology has clear documentation on how to configure UPS service, including:

  • USB UPS

  • SNMP UPS

  • and use the NAS as a server to notify other devices ( UPS server / network UPS server )

Recommended bandwidth (USB – most common):

  1. Connect the UPS to the NAS via USB.

  2. In DSM, enable UPS support.

  3. Define "battery time" before entering standby/shutdown mode.

  4. (Optional) Enables the NAS as a UPS Server to disconnect other clients on the network.

When to use SNMP:

  • Do you have a rack, multiple devices, or a UPS with a network card?

  • You want centralized monitoring and management.
    Synology allows you to configure SNMP UPS on the UPS panel.

5) "Uninterruptible Power Supply (UPS) Server and Multiple Devices: How to Do It Right

If you want:

  • Turn off the NAS.

  • and that PCs/servers also shut down safely,

It makes sense to keep the network active during the event (router/switch on the UPS). Otherwise, notifications may not reach customers in time.

6) Sine wave: do I need it for NAS?

Many NAS devices and switches work well with simulated wave UPS systems, but if:

  • The NAS has a more demanding power supply.

  • There is active PFC,

  • Or do you want maximum compatibility?

Consider UPS with pure sine wave (we discuss this in detail in article 3). Schneider recommends pure sine wave for maximum compatibility with power supplies with active PFC and sensitive electronics.

7) Purchase checklist (UPS for NAS/server)

  1. Capacity : sum of watts + margin

  2. Communication : USB (minimum) or SNMP (ideal)

  3. DSM configuration : UPS support + shutdown time

  4. Network connection via UPS : Router/switch via UPS for notifications (if applicable)

  5. Replaceable battery : consider the cost and availability of the cartridge.

FAQ

USB is sufficient, or do I need SNMP?
USB is sufficient for 1 NAS + simple shutdown. SNMP is better for racks, multiple devices, and monitoring.

Can I use the NAS to disconnect other devices on the network?
Yes, Synology supports "UPS server / network UPS server" mode for clients on the network.