Network Attached Storage (NAS) devices are the backbone of home and small business data storage. Buying a used NAS can save significant money, but these devices contain complex storage systems that require careful evaluation. From drive health and RAID integrity to network performance and software capabilities, this comprehensive guide will help you thoroughly test any NAS before purchase. Whether you're looking at Synology, QNAP, Asustor, or other brands, these procedures will protect your data and investment.
Important: NAS devices often come without drives. Clarify whether drives are included, and if so, their age, capacity, and type. Drive value can exceed the NAS enclosure value.
Understanding NAS Devices
A NAS is essentially a specialized computer designed for file storage and sharing. Understanding the key components helps you evaluate what you're buying.
Enclosure (Diskless)
The NAS box without drives. Contains CPU, RAM, network ports, and software. You add your own drives.
Populated NAS
NAS with drives included. Check drive health carefully—this is often where problems hide.
Bay Count
Number of drive slots: 2-bay for home use, 4-8 bay for prosumer/SMB, 12+ for enterprise.
Plus Series vs Value
Plus/Pro models have faster CPUs, more RAM, and features like Docker, VMs, and 10GbE support.
Key Specifications
- CPU: Intel Celeron/Atom for basic use, Intel Core or AMD Ryzen for transcoding and VMs
- RAM: 2GB minimum, 4GB+ for apps/Docker, 8GB+ for VMs
- Network: 1GbE standard, 2.5GbE becoming common, 10GbE for power users
- M.2 slots: For SSD caching or storage pools on newer models
Physical Inspection
NAS devices live in closets, under desks, and in dusty environments. Physical condition reveals how well it was maintained.
External Inspection
- • Check all fan vents for dust buildup or blockage
- • Examine drive trays for damage or missing clips
- • Test all USB ports for physical damage
- • Verify network port indicator LEDs work
- • Check power jack for damage or loose fit
- • Look for rust or corrosion (humidity damage)
Drive Bay Inspection
Remove drive trays and inspect the SATA backplane connections. Look for bent pins, corrosion, or damage. Verify all drive bay locks function properly. Hot-swap bays should release and insert drives smoothly.
Fan and Cooling
Fans are common failure points. Power on the NAS and verify all fans spin. Listen for grinding, clicking, or excessive noise. Replacement fans are usually available, but noisy fans indicate potential thermal issues.
Drive Health Assessment
If the NAS includes drives, their health is critical. Drives are the most likely component to fail and can contain hidden problems.
S.M.A.R.T. Data Review
Access the NAS management interface (DSM for Synology, QTS for QNAP) and navigate to Storage Manager > HDD/SSD. Check the S.M.A.R.T. status and detailed attributes for each drive.
Critical Warning: Drives showing "Warning" or "Critical" S.M.A.R.T. status should not be purchased. Even "Normal" status doesn't guarantee reliability—check specific attributes.
Critical S.M.A.R.T. Attributes
- • Reallocated Sector Count: Should be 0 or very low. High count indicates dying drive.
- • Current Pending Sector Count: Sectors waiting to be reallocated. Should be 0.
- • Uncorrectable Sector Count: Bad sectors that can't be fixed. Should be 0.
- • Power-On Hours: Total running time. 40,000+ hours indicates heavy use.
- • Load/Unload Cycle Count: Head parking cycles. Very high counts on SMR drives are concerning.
Drive Age and Model
Identify drive models and look up their specifications. NAS-rated drives (WD Red Plus/Pro, Seagate IronWolf) are designed for 24/7 operation. Desktop drives in a NAS may have shortened lifespans. Check power-on hours to estimate actual usage.
RAID Status Verification
RAID provides data redundancy, but a degraded RAID array is a ticking time bomb. Understanding the RAID status is essential.
Understanding RAID Status
Healthy Status
- • "Normal" or "Healthy" status
- • All drives showing green
- • No rebuild in progress
- • Capacity matches expectation
Problem Indicators
- • "Degraded" status (drive failed)
- • "Rebuilding" (array repairing)
- • "Critical" (data at risk)
- • Missing or failed drives
RAID Type Considerations
Different RAID types offer different trade-offs. Verify the RAID type meets your needs:
- RAID 1: Mirror—2 drives, 1 drive capacity, survives 1 failure
- RAID 5: Parity—3+ drives, loses 1 drive capacity, survives 1 failure
- RAID 6: Dual parity—4+ drives, survives 2 failures (recommended)
- SHR/SHR-2: Synology Hybrid RAID—flexible drive sizes, 1-2 drive redundancy
Network Testing
Network performance is why you buy a NAS instead of external drives. Test all network ports and verify expected speeds.
Port Testing
Connect an Ethernet cable to each port individually and verify link establishment. All ports should achieve their rated speed (check router/switch for link speed). Multi-port NAS models support link aggregation for higher throughput.
Expected Link Speeds
- • 1GbE: 1000 Mbps—standard, ~110-115 MB/s max throughput
- • 2.5GbE: 2500 Mbps—growing standard, ~280-300 MB/s max
- • 10GbE: 10000 Mbps—prosumer/enterprise, ~1100-1200 MB/s max
Speed Test
Transfer a large file (1GB+) to and from the NAS. Measure actual transfer speeds. On 1GbE, expect 100-115 MB/s. Significantly lower speeds may indicate network issues, drive problems, or CPU limitations during encryption.
Software & Feature Testing
NAS software ecosystems vary significantly. Test the features you plan to use.
Operating System Update
Check the current OS version and whether updates are available. Older NAS models may no longer receive security updates—verify the model is still supported. Update to the latest version during testing to verify the update process works.
Key Features to Test
- File sharing: SMB, AFP, NFS—test from your computers
- Media server: Plex, Emby, Jellyfin—test transcoding if you need it
- Docker/Container support: Essential for modern self-hosting
- Backup solutions: Time Machine, Active Backup, Hyper Backup
- Remote access: QuickConnect, DDNS, VPN server
Performance Testing
NAS performance depends on CPU, RAM, drives, and network. Test under realistic workloads.
Benchmark Testing
Use tools like CrystalDiskMark (mapping a network drive) or iperf3 for pure network testing. Sequential read/write speeds should approach your network limit. Random I/O performance varies by drive type and RAID configuration.
Expected Performance (1GbE)
- • Sequential read: 100-115 MB/s
- • Sequential write: 100-115 MB/s
- • Random read: 20-100 MB/s (varies by drive)
- • Random write: 15-80 MB/s (varies by RAID)
Multi-Client Testing
If possible, have multiple devices access the NAS simultaneously. Performance should scale reasonably without dramatic slowdowns or disconnections.
Power Consumption & Noise
NAS devices run 24/7. Power consumption and noise matter for home environments.
Power Testing
Use a Kill-A-Watt or similar meter to measure power consumption. Check idle power (drives sleeping) and active power (during file transfers). Compare to manufacturer specifications—significantly higher consumption may indicate failing components.
Typical Power Consumption
- • 2-bay idle: 10-20W
- • 4-bay idle: 25-40W
- • 2-bay active: 20-35W
- • 4-bay active: 40-70W
Noise Assessment
Listen to the NAS during various states: boot, idle, and heavy disk activity. Fan noise and drive clicking are normal; grinding, whining, or rattling are not. If the NAS will be in a living area, noise matters significantly.
Data Ownership & Transfer
Understand what happens with existing data and ensure clean transfer of ownership.
Data Handling Options
- Factory reset: Seller performs full reset, you start fresh (recommended)
- Keep configuration: You inherit settings but should change all passwords
- Diskless purchase: Buy enclosure only, add your own drives (cleanest option)
Security Note: After purchasing, always change all passwords, check for unauthorized users, review shared folder permissions, and disable any unknown services or remote access configurations.
2026 NAS Pricing Guide
NAS prices vary by brand, bay count, and features. These are enclosure-only prices (diskless).
| Model | MSRP | Used (Good) | Buy New |
|---|---|---|---|
| Synology DS223j (2-bay) | $189 | $120-150 | - |
| Synology DS224+ (2-bay) | $349 | $250-300 | Buy on Amazon |
| Synology DS423+ (4-bay) | $549 | $380-450 | - |
| Synology DS923+ (4-bay) | $599 | $420-500 | Buy on Amazon |
| QNAP TS-264 (2-bay) | $399 | $260-320 | - |
| Asustor Drivestor 4 Pro (4-bay) | $349 | $240-300 | Buy on Amazon |
| QNAP TS-464 (4-bay) | $549 | $380-450 | Buy on Amazon |
Add $50-200 per included NAS-grade drive depending on capacity. Drives significantly affect total value.
Recommended NAS Hard Drives
NAS-rated drives are designed for 24/7 operation, vibration tolerance, and RAID compatibility. These are the top choices for reliable storage.
WD Red Plus 8TB
CMR technology, ideal for home and small business NAS. 5640 RPM, up to 8 bays, 180 TB/yr workload.
Buy on AmazonSeagate IronWolf 8TB
AgileArray technology, optimized for multi-bay NAS. 7200 RPM, up to 8 bays, 180 TB/yr workload.
Buy on AmazonFinal Testing Checklist
Use this interactive checklist during your evaluation. All critical items should pass before purchasing.
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