A Complete Guide to NAS Devices (2025)

Whether you're consolidating family photos, running Plex, or building a small office file server, choosing the right Network Attached Storage (NAS) setup determines how easily data is stored, shared, and protected. This guide covers architecture, planning, and technical decisions. For hardware recommendations, see Best NAS Devices. To evaluate costs and ROI, check Are NAS Devices Worth It?. When you're ready to deploy, follow How to Set Up NAS Devices. For backup strategies, use the NAS Data Protection Guide.

Three questions to start:

1. What data needs protecting? Family photos, media library, work files, or all of the above?
2. How many people will use it? Just you, your household, or a small team?
3. What apps will run on it? Just file storage, or also Plex, Docker containers, surveillance, or virtual machines?

Your answers determine which NAS to buy:

For households (1-5 users):

• Basic file backup and photo sharing: 2-4 bay NAS with standard networking
• Plex media server: 4-bay NAS with hardware transcoding, consider 2.5GbE networking
• Advanced users running Docker: 4-bay NAS with NVMe cache and 8GB+ RAM

For small offices (5-15 users):

• Basic file sharing: 4-bay NAS with 2.5GbE networking
• Multiple simultaneous users: 4-6 bay NAS with 2.5GbE or 10GbE
• Creative work (video editing, CAD): 6-8 bay NAS with 10GbE or Thunderbolt

For power users and studios:

• Large media libraries or heavy virtualization: 8+ bay NAS with dual 10GbE
• Mission-critical data: DIY build with ECC RAM and enterprise features

Three essentials before you buy anything else:

1. Uninterruptible Power Supply (UPS): Protects against data loss during power outages. Size by runtime, not just volt-amps. Measure your load in watts, choose a UPS with a watt rating at least 2x that load, then check the vendor's runtime chart for 10-20 minutes. Example: 120W total (NAS + switch) requires a 600-1000VA unit in most cases.

2. Off-site backup plan: Cloud storage or second NAS at another location
3. Secure remote access: VPN or vendor-provided secure relay, never direct internet exposure

The basics:

A NAS is a dedicated file server connected to your network via Ethernet. It makes folders (called "shares") available to all your devices so everyone accesses the same files from one central location.

How data is protected:

Multiple hard drives combine into a storage array using RAID. RAID spreads your data across multiple drives so that if one drive fails, you don't lose anything. Common configurations:

• RAID 1 (Mirror): Two drives with identical copies. One drive can fail without data loss.
• RAID 5: Three or more drives. Any single drive can fail safely. Good for 4-bay NAS units.
• RAID 6: Four or more drives. Any two drives can fail safely. Recommended for larger drives (12TB+).
• SHR/TRAID: Vendor-specific flexible RAID that simplifies mixing drive sizes (Synology SHR, TerraMaster TRAID).

Important: Keep 20-30% of your storage free. This helps the NAS rebuild drives faster if one fails and keeps performance smooth.

The filesystem is how your NAS organizes and protects data. For most users, your NAS vendor chooses this for you:

Btrfs (many pre-built NAS units):

• Common on Synology and UGREEN. QNAP typically uses ext4 with QTS or ZFS with QuTS hero.
• Built-in snapshots, data checksums, and self-healing when used with redundancy
• Low memory requirements that work well with 4-8GB RAM
• Best for: Home users, small offices, anyone wanting snapshot protection with integrity features

ext4 (simple and proven):

• Minimal overhead, broad compatibility, very reliable
• No built-in snapshots or checksums
• Used by QNAP QTS and some lightweight NAS builds
• Best for: External backup drives, simple file storage, maximum performance on older hardware

ZFS (advanced users and businesses):

• Maximum data integrity with built-in error detection
• Powerful snapshot and replication features
• Higher memory requirements that scale with capacity and features
• Used by TrueNAS, QNAP QuTS hero, and advanced DIY builds
• Best for: Mission-critical data or users who want complete control

Most home users should stick with whatever filesystem their NAS vendor provides. Choose ZFS if you're building a custom NAS or buying a ZFS-based system and want enterprise-grade data protection.

Memory requirements:

• Base requirement: 8-16GB for typical home or small office use
• ECC RAM strongly recommended to detect and correct memory errors
• Larger pools or heavy workloads: 16-32GB or more for better ARC cache performance
• Deduplication: Niche feature. Avoid unless required. Expect significant RAM needs (roughly 1-5GB per TB of deduplicated data) and possible slowdown on mixed workloads

Advanced features:

• RAIDZ: ZFS parity arrays that improve data integrity compared to traditional RAID
• Send and receive replication: Native backup to a second NAS
• Special vdevs: Store metadata on NVMe for faster small-file access. Must be mirrored because metadata loss destroys the entire pool
• Self-healing: With redundancy, ZFS detects and corrects silent corruption

Many NAS units offer NVMe SSD slots for caching. This speeds up access to frequently used files but isn't essential for most users.

Read cache (safe and simple):

• Uses one NVMe drive to speed repeated file access
• Great for photo libraries, Plex thumbnails, frequently accessed documents
• If the cache drive fails, nothing is lost. The NAS just runs slower until you replace it
• Recommended for: Plex servers, photo libraries, Docker containers

Write cache (requires caution):

• Temporarily stores writes on NVMe before moving to hard drives
• Faster performance but risks data loss if the cache drive fails
• Critical safety rule: Use two NVMe drives mirrored for write caching and prefer models with power-loss protection
• Most home users should skip write caching or use read-only caching

• Special vdev: Stores metadata on NVMe for small-file performance. Must be mirrored and should use enterprise NVMe with power-loss protection
• SLOG (ZFS Intent Log): Speeds synchronous writes for databases and VMs. Mirror it and use PLP-equipped enterprise NVMe to protect writes during power loss

Modern NAS devices run applications directly:

• Media servers: Plex, Jellyfin, Emby
• Containers: Docker for self-hosted apps
• Surveillance: Security camera recording and monitoring
• Backups: Automated computer backup software
• Virtual machines: Run Linux or Windows VMs on capable hardware

Budget extra RAM (at least 16GB) and consider NVMe cache if running multiple services simultaneously.

Pre-built NAS units come with vendor software that makes setup simple. DIY builds let you choose your operating system for more control.

For most users (pre-built NAS):

• Synology DSM: Polished interface, strong apps, excellent documentation. Recent models have restored broad third-party HDD compatibility. Some M.2 NVMe pool restrictions still apply on certain models
• UGREEN UGOS Pro: Modern UI, AI photo features, good hardware value on NASync series
• QNAP QTS: Rich app selection, balanced features

For advanced users (DIY builds):

• TrueNAS SCALE: Enterprise ZFS features, full virtualization, open source
• Unraid: Flexible drive expansion, strong community plugins. Current licensing includes Basic, Plus, and Pro tiers

Feature	Synology DSM	UGREEN UGOS Pro	TrueNAS SCALE	Unraid
Best for	Most home or office users	Modern hardware value	Enterprise or power users	Flexible expansion
Ease of use	Excellent	Good	Requires technical knowledge	Moderate
Docker support	Yes	Yes	Full plus Kubernetes	Yes
Filesystem	Btrfs	Btrfs	ZFS	XFS by default with plugin options
Snapshots	Built-in	Built-in	Advanced ZFS snapshots	Plugin or app based
Cost	Included with hardware	Included with hardware	Free	Paid licensing
VM support	Basic to moderate	Limited to moderate	Full KVM with GPU passthrough	Full GPU passthrough

Quick recommendations:

• Easiest: Synology for polished experience and best documentation
• Best value hardware: UGREEN for 10GbE and NVMe options at competitive prices
• Most powerful: TrueNAS SCALE for ZFS and enterprise features if you have the skills
• Most flexible: Unraid for easy drive expansion and community support

How many drive bays do you need?

Most users should start with their storage needs and add 50% headroom:

• 2 bays: 4-8TB usable for family photos, documents, basic backup
• 4 bays: 10-24TB usable for media libraries, home office, Plex server
• 6-8 bays: 30-80TB usable for creative work, small business, heavy media

Simple bay count guide:

• 2-4 bays: Families, home users, small media libraries
• 4-6 bays: Plex servers, photographers, small offices
• 6-8 bays: Video editors, businesses, large media collections
• 8+ bays: Professional studios, many users or heavy virtualization

Capacity planning:

Keep 20-30% of storage free. This is especially helpful on copy-on-write filesystems like Btrfs and ZFS to reduce fragmentation and speed rebuilds.

Drive selection guidance:

Prefer CMR drives for arrays over SMR. SMR drives have poor sustained write performance and can cause long rebuilds or timeouts. Choose NAS-rated or enterprise drives:

• Seagate IronWolf Pro 8TB: 7200 RPM, 256MB cache, CMR, 300-550TB/year workload, 1.2-2M hour MTBF, 5-year warranty with data recovery

• WD Red Pro 16TB: 7200 RPM, 512MB cache, CMR, helium-filled, 550TB/year workload, 2.5M hour MTBF, 5-year warranty

• Toshiba N300 16TB: 7200 RPM, 512MB cache, CMR, 180TB/year workload, 1M hour MTBF, 3-year warranty

Setup	Protection Level	Usable Storage	Best For
2-bay RAID1	1 drive can fail	50%	Beginners, essential data
4-bay RAID5	1 drive can fail	75%	Most home users
4-bay RAID6	2 drives can fail	50%	Larger drives 12TB+
6-bay RAID6	2 drives can fail	67%	Small business, creative
8-bay RAID6	2 drives can fail	75%	Large drives 18TB+, production use

Simple rule: Use RAID6 for any array with 12TB or larger drives.

Unrecoverable Read Errors can interrupt RAID rebuilds, especially with large drives.

Typical URE rates:

• Consumer HDDs: 1 error in 10^14 bits read (about 12.5TB)
• Enterprise HDDs: 1 error in 10^15 bits (about 125TB)

Why RAID6 helps: Dual parity tolerates a URE during rebuild as a second failure, allowing the process to complete.

Mitigation strategies:

• Use RAID6 for 12TB+ drives
• Prefer NAS-rated or enterprise drives with better URE specs
• Keep storage under 70% full to reduce rebuild stress and time
• Run monthly scrubs to detect and repair errors early
• Maintain off-site backups because RAID protects availability, not data

For most home users: Keep one matching cold spare. Replace manually when a drive fails.

For larger arrays or business use: A cold spare is still cost effective for 8+ bays and 18TB+ drives where rebuilds are long.

Hot spares: Useful on enterprise gear but rarely needed at home.

Budget planning examples:

• Small household with 2-3 users: 8-12TB usable
• Plex plus family photos: 20-30TB usable
• Creative work or small business: 48-72TB usable

Start with layered protection:

• Schedule snapshots on every critical share and practice restores
• Follow the 3-2-1 rule: three copies, two media types, one off-site or immutable
• Automate health checks. Configure SMART testing, scrubs, and alerting before you load production data

Operational discipline keeps things smooth. Document bay assignments, firmware levels, and replacement procedures. Stage firmware or app upgrades behind current snapshots. Audit alert delivery monthly so notifications still reach your inbox or chat tool. See the setup guide for the complete operating flow and maintenance schedule.

Hardware: 4-bay NAS, RAID5 or SHR, four 10TB CMR drives (about 27TB usable), 2.5GbE networking.

Recommended NAS options:

• UGREEN DXP4800: Intel N100, 8GB DDR5, dual 2.5GbE, 4 bays, 2x NVMe slots, Intel Quick Sync for transcoding

• Synology DS223: ARM CPU, 2GB DDR4, 1GbE, 2 bays, Btrfs snapshots, excellent DSM software

Setup: Dedicated share for RAW shoots, separate archive share for completed projects. Enable hourly snapshots on active work with 24-hour retention and daily snapshots on archives with 30-day retention. Use a local SSD for the Lightroom catalog with RAW files on the NAS.

Backup: Replicate snapshots to Backblaze B2 nightly. Keep one cold spare 10TB drive on the shelf.

Bottleneck to watch: Network speed when culling hundreds of RAW files. Enable NVMe read cache or upgrade to 10GbE if browsing thumbnails lags.

Hardware: 8-bay NAS, RAID6 or RAIDZ2, eight 12TB CMR drives (about 72TB usable), dual 10GbE, 32GB RAM, NVMe cache.

Recommended hardware:

• UGREEN DXP8800 Plus: Intel i5-1235U, 8GB DDR5, dual 10GbE, dual Thunderbolt 4, 8 bays, 4x NVMe slots

• QNAP TS-832PX-4G: ARM CPU, 4GB DDR4, dual 10GbE SFP+ + dual 2.5GbE, PCIe slot, 8 bays

• WD Red Pro 16TB drives: 7200 RPM, CMR, helium-filled, ideal for RAID6 arrays

Setup: Project share for active edits with proxies on an SSD or NVMe tier and camera originals on HDD. Mount via NFS for Linux or SMB for Windows and macOS. Allocate headroom for Docker-based proxy generators.

Backup: Replicate finished projects to a second NAS at another location. Use LTO tape for long-term archives if budget allows.

Bottleneck to watch: Simultaneous editor count. Plan roughly 500 MB/s per editor working with high bitrate 4K. Add link aggregation or upgrade to 25GbE if more than four editors work concurrently.

Hardware: 4-bay NAS, RAID6 or SHR-2, four 12TB CMR drives (about 24TB usable), 2.5GbE, 16GB RAM.

Recommended hardware:

• UGREEN DXP4800: Intel N100, 8GB DDR5, dual 2.5GbE, Intel Quick Sync, snapshots, modern UGOS Pro

• ASUSTOR AS6804T: AMD Ryzen V3C14, 16GB ECC DDR5, dual 10GbE + dual 5GbE, dual USB4, 4x NVMe slots

• WD Red Pro 16TB drives: Reliable CMR drives for business-critical data with 5-year warranty

Setup: Separate shares for Finance with restricted access and immutable snapshots, HR with restricted access, Projects with team access and versioning, Backups for automated workstation backups. Integrate with Active Directory or LDAP.

Backup: Replicate snapshots to Wasabi with 90-day retention. Keep quarterly financials on immutable storage for seven years.

Bottleneck to watch: Concurrent users during peak hours. Monitor CPU and RAM utilization. Add NVMe cache if small-file operations slow down.

Network speed basics:

Your NAS is only as fast as your network.

• 1 Gigabit Ethernet: about 110 MB/s
• 2.5 Gigabit Ethernet: about 280 MB/s
• 10 Gigabit Ethernet: about 1,000 MB/s

When to upgrade from 1GbE:

• Frequent large transfers of 100GB or more
• Multiple users accessing at once
• Video editing directly from the NAS
• VMs or containers with high I/O

Important: Faster networking doesn't help if your storage is slower. A single HDD tops out near 150-180 MB/s. Higher network speeds shine with multiple drives, SSDs, or NVMe caching.

What you need for faster networking:

• NAS with matching ports such as 2.5GbE or 10GbE
• A network switch that supports the same speed
• Cables: Cat 5e is fine for 2.5GbE. Use Cat 6a for 10GbE copper. Cat 6 may work for short runs under 55 meters but Cat 6a is the reliable spec
• Client devices with matching adapters
• Consider SMB Multichannel for single-client speed boosts if your OS and drivers support it. Test stability before production

For remote access, use a VPN such as WireGuard or your vendor's secure option. Never expose your NAS admin interface directly to the internet.

No. RAID protects against drive failure, not data loss.

RAID keeps your NAS running when a drive fails, but it doesn't protect against accidental deletion, ransomware, corruption, theft, fire, flood, or user error.

The 3-2-1 backup rule:

• 3 copies of your data
• On 2 different media such as NAS plus cloud or NAS plus external drive
• 1 copy off-site or immutable

Enable snapshots for quick recovery from accidental changes, then add cloud backup or a second NAS at another location.

Most home users should start with 2.5GbE instead.

Stick with 1GbE if:

• You mostly access documents and photos
• Single-user household with occasional large transfers
• Budget is tight

Upgrade to 2.5GbE if:

• Multiple users access the NAS at once
• Frequent large file transfers
• Running Plex or similar servers
• Works with existing Cat 5e cables

Step up to 10GbE if:

• Editing 4K or higher video directly on the NAS
• Business with 5 or more simultaneous users
• VMs or containers with heavy I/O

Remember: Your storage must keep up. A single HDD at 150 MB/s won't saturate 10GbE.

Quick recommendations:

• 2 bays: Minimal protection for modest needs
• 4 bays: Sweet spot for most home users
• 6-8 bays: Small business or creative professionals
• 8+ bays: Professional studios, heavy virtualization, enterprise use

Plan for 3-5 years of growth and keep 20-30% free space.

Yes, but methods vary by platform.

Replace drives one by one: Most systems let you swap for larger drives and expand after all are replaced.

Add new drive groups: Some platforms such as Unraid allow adding individual drives or groups.

Important considerations:

• Expansion can take a day or two for large arrays
• Always back up before expanding
• Follow your vendor's expansion guide
• Some systems require matching drive sizes

Yes, when configured properly.

Essential steps:

• Change default admin credentials and disable or rename the default admin account
• Use strong unique passwords and enable MFA
• Enable account lockout after failed attempts
• Keep firmware and apps updated on a schedule
• Use VPN for remote access. Don't expose the admin panel
• Disable UPnP on your router
• Disable unused services and protocols
• Create regular snapshots with tested retention policies

Advanced security:

• Enable volume encryption at rest and store recovery keys off-site
• Use immutable or air-gapped backups
• Monitor logs and send alerts to email or remote syslog
• Restrict access by user and folder with least-privilege principles
• Test disaster recovery procedures twice per year

A properly secured NAS offers strong control over access and encryption and can be safer than ad hoc use of public cloud storage for sensitive data.

Quick reference for terms used throughout this guide. Short, beginner-friendly definitions.

• 3-2-1 Backup Rule: Keep 3 copies of data on 2 different types of storage with 1 copy off-site or immutable. This protects against total loss from theft, fire, or ransomware.
• Btrfs: A modern filesystem with checksums and snapshots for quick rollbacks. Self-healing works when redundancy is present. Common on Synology and UGREEN.
• CMR vs SMR Drives: Conventional Magnetic Recording writes tracks separately and performs well in RAID. Shingled Magnetic Recording overlaps tracks to fit more data but slows during heavy writes or rebuilds. Choose CMR for NAS arrays.
• Docker Containers: Lightweight packaged apps that run services on your NAS with minimal overhead. Easier to manage than full virtual machines for most add-ons.
• Drive Bay: The slot where a hard drive or SSD installs. More bays allow more capacity and stronger redundancy. Four bays fit most homes.
• ext4: A proven, fast filesystem for simple storage. No native snapshots or checksums. Good for lightweight or legacy setups.
• GbE (Gigabit Ethernet): Network link speed. Real-world transfers are about 110 MB/s on 1 GbE, 260 to 290 MB/s on 2.5 GbE, and 800 MB/s to 1,050 MB/s on 10 GbE with capable storage.
• NAS-Rated Drives: Hard drives built for 24/7 multi-drive use with vibration tolerance and RAID-friendly firmware. Examples include Seagate IronWolf and WD Red Plus or Pro.
• NVMe Cache: Fast SSD storage used to accelerate frequent reads or writes. Read cache is simple and safe. Write caching needs two drives in a mirror and power-loss protection.
• RAID: Redundant Array of Independent Disks. Combines drives for uptime and performance. RAID 1 mirrors data, RAID 5 tolerates one drive failure, RAID 6 tolerates two. RAID is not a backup.
• RAIDZ: ZFS parity layouts similar to RAID 5 or 6 with end-to-end checksums for stronger data integrity. Suited to advanced or DIY builds.
• SMB Multichannel: Uses multiple equal-speed network links between one client and the NAS to boost a single transfer. Supported by modern Windows and many NAS OSes. Test stability before production use.
• Snapshots: Instant, read-only views of a filesystem at a point in time. Great for quick recovery from mistakes or ransomware. Pair with backups for full protection.
• UPS (Uninterruptible Power Supply): A battery that keeps the NAS running long enough to shut down safely. Size for about 10 to 20 minutes at your measured load and connect via USB for automatic shutdown.
• URE (Unrecoverable Read Error): A sector read that permanently fails. During a rebuild it can derail RAID 5. Larger drives raise exposure. Dual-parity arrays and regular scrubs reduce risk.
• Virtual Machines (VMs): Full operating systems running on the NAS. Useful for lab or specialty apps. Plan on 16 GB or more RAM for smooth performance.
• ZFS: An advanced filesystem with checksums, snapshots, and efficient replication. Excellent integrity and features, but it benefits from more memory, often 8 to 16 GB or higher.