QNAP TS-251D - User Manual

Kayla StanleyJul 27, 2025

What to do if hot-swapping failed drives on QNAP TS-251D Storage?

H
Henry PowellJul 27, 2025
To replace a failed drive, log on to QTS, then go to Main Menu > Storage Manager > Storage > Disks/VJBOD. Locate the failed drive. Prepare a new hard drive with a capacity that is the same as or larger than the failed hard drive. Remove the failed drive from the NAS. Wait for 20 seconds or until the NAS beeps twice. Remove the failed drive from the drive tray. Insert the new drive into the drive tray, and then install the new drive.

QNAP TS-251D Specifications

General

Type	NAS
Noise level	16.7 dB
Device class	Home & Home Office
Share folder	CIFS/SMB, FTP, WebDAV
Backup features	Cloud, USB drive
Backup function	Yes
Browser supported	Apple Safari 7+, Google Chrome, Microsoft Internet Explorer 10+, Mozilla Firefox
Security algorithms	256-bit AES, FIPS 140-2, SNMPv3, SSH, SSL/TLS
Storage temperature (T-T)	-20 - 70 °C
Operating temperature (T-T)	0 - 40 °C
Operating relative humidity (H-H)	5 - 95 %
Chassis type	Tower
Cooling type	Active
Fan diameter	70 mm
Product color	White
LED indicators	HDD, LAN, Power, Status, USB
Number of fans	1 fan(s)
Cable lock slot type	Kensington
Fiber ports quantity	0
USB 2.0 ports quantity	3
USB 3.2 Gen 1 (3.1 Gen 1) Type-A ports quantity	2
Wi-Fi	No
Ethernet LAN data rates	1000 Mbit/s
Supported network protocols	TCP/IP, PTP, L2TP/IPSec, OpenVPN, QBelt(, FTP, SFTP, TFTP
Flash memory	4000 MB
Internal memory	4 GB
Memory form factor	SO-DIMM
Internal memory type	DDR4
Maximum RAM supported	8 GB
Cables included	AC, LAN (RJ-45)
Number of screws	14
Tjunction	105 °C
Processor cache	4 MB
Processor model	J4005
System bus rate	- GT/s
Processor family	Intel® Celeron®
Processor socket	BGA 1090
Processor codename	Gemini Lake
Processor frequency	2 GHz
Processor lithography	14 nm
Processor manufacturer	Intel
Processor package size	25 x 24 mm
Processor boost frequency	2.7 GHz
Processor operating modes	64-bit
PCI Express configurations	1x2, 1x2+2x1, 1x4, 2x1, 4x1
Thermal Design Power (TDP)	10 W
On-board graphics card model	Intel® UHD Graphics 600
Fan voltage	12 V
AC input voltage	100 - 240 V
AC input frequency	50 - 60 Hz
Power supply location	External
Power consumption (sleep)	8.08 W
Power consumption (typical)	15.25 W
Power supply unit (PSU) capacity	65 W
Operating system version	5.0.0
Operating system installed	QNAP QTS
Mac operating systems supported	Mac OS X 10.10 Yosemite, Mac OS X 10.11 El Capitan, Mac OS X 10.12 Sierra, Mac OS X 10.13 High Sierra, Mac OS X 10.14 Mojave, Mac OS X 10.15 Catalina, Mac OS X 10.7 Lion, Mac OS X 10.8 Mountain Lion, Mac OS X 10.9 Mavericks
Server operating systems supported	Windows Server 2003, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2, Windows Server 2016, Windows Server 2019
Windows operating systems supported	Windows 10, Windows 7, Windows 8
RAID levels	0, 1, JBOD
Storage drive size	- \
Storage drive capacity	0 GB
Supported file systems	FAT32, HFS+, NTFS, ext3, ext4
Storage drive interface	-
Storage drive sizes supported	3.5 \
Supported storage drive types	HDD & SSD
Total installed storage capacity	0 TB
Supported storage drive interfaces	Serial ATA II, Serial ATA III
Number of execution units	12
Maximum number of PCI Express lanes	6
Memory types supported by processor	DDR4-SDRAM, LPDDR4-SDRAM
Intel Smart Response Technology version	0.00
Intel Identity Protection Technology version	1.00
On-board graphics card ID	0x3185
On-board graphics card base frequency	250 MHz
On-board graphics card DirectX version	12.0
On-board graphics card dynamic frequency (max)	700 MHz
Processor ARK ID	128992
Harmonized System (HS) code	84714100

Weight and Dimensions

Depth	226 mm
Width	105 mm
Height	168 mm
Weight	1480 g
Package weight	2580 g

Summary

1. Preface

About This Guide

Provides information on the QNAP TS-251D NAS and step-by-step instructions.

Audience

Intended for consumers and storage administrators with basic storage knowledge.

Document Conventions

Explains symbols used in the guide for notes, important information, tips, and warnings.

2. Product Overview

About the TS-251 D

Details the TS-251D's processor, RAM support, USB features, and encryption engine.

Hardware Specifications

Lists ordering P/N, CPU, memory, power supply, and component details of the NAS.

Storage

Details drive bays, compatibility, SSD cache, hot-swapping, network, PCIe, and USB ports.

HDMI ports, Interface, IR sensor, Buttons

Describes HDMI output, IR sensor, and basic buttons like Power, Reset, and USB One Touch Copy.

Dimensions

Provides form factor and physical dimensions (H x W x D) of the NAS.

Package Contents

Lists the items included in the NAS package.

Components

Front Panel

Identifies and explains the components and LEDs on the front panel of the NAS.

Left Panel

Identifies PCIe and memory slots on the left side of the NAS.

Rear Panel

Identifies Ethernet port, LEDs, security slot, HDMI, USB, DC IN, and Reset button.

Safety Information

General Instructions

Provides general safety and environmental instructions for handling the NAS.

Environment

Specifies required room temperature, humidity, and surface conditions for NAS installation.

Hardware and peripherals

Lists required hardware like storage drives, network cables, and tools for installation.

Tools

Lists necessary tools like screwdrivers and an anti-static wrist strap.

3. Installation and Configuration

Hardware Installation

Provides information on installing drives, memory modules, and expansion cards.

Drive Installation

Explains compatibility with different drive types and the process of installing them.

Installing 3.5-inch Hard Drives on 3.5-inch Trays

Step-by-step instructions for installing 3.5-inch hard drives onto the NAS trays.

Installing 2.5-inch Hard Drives or Solid-State Drives on 3.5-inch Trays

Step-by-step instructions for installing 2.5-inch drives onto the NAS trays.

QTS Installation

Qfinder Pro installation (Recommended)

Instructions for installing QTS using Qfinder Pro on a local network.

Cloud installation

Instructions for installing QTS via the internet using a QR code and Cloud Key.

Local installation

Instructions for installing QTS using HDMI output with a monitor and keyboard.

Installing QTS Using Qfinder Pro

Step-by-step guide for installing QTS via Qfinder Pro, including NAS naming.

Installing QTS Using the Cloud Key

Steps to install QTS using a Cloud Key via the internet.

Installing QTS Using an HDMI Connection

Steps to install QTS using an HDMI display, keyboard, or remote control.

4. Basic Operations

Power Button

Explains how to power the NAS on, off, and force power off.

Reset Button

Details basic and advanced system reset procedures and their effects.

LEDs

Explains the status indications provided by the NAS LEDs.

Audio Alert

Describes the different audio alerts and their meanings.

5. Troubleshooting

Forcing Qfinder Pro or myQNAPcloud to Locate the NAS

Steps to resolve issues where Qfinder Pro cannot locate the NAS during installation.

Hot-Swapping Failed Drives

Procedure for replacing a failed drive in a RAID 1 configuration without downtime.

Recovering Unintentionally Removed Healthy Drives

Explains RAID recovery technology for unintentional drive removal.

Support and Other Resources

Provides URLs for documentation, service portal, downloads, and community forum.

6. Glossary

QNAP Cloud Services

Definitions for CloudKey, myQNAPcloud Link, myQNAPcloud, and myQNAPcloud ID.

QNAP Utilities

Definitions for Qfinder Pro and QTS.

7. Notices

Limited Warranty

Information on the QNAP product warranty period and terms.

Disclaimer

Legal disclaimer regarding the document's information and QNAP's liability.

GNU Public License

Details the terms and conditions of the GNU General Public License.

CE Notice

FCC Notice

States compliance with FCC Part 15 rules for Class B digital devices.

VCCI Notice

Indicates compliance with BSMI standards and RoHS regulations.