Why You Should Test Your NAS Speed
A NAS (Network Attached Storage) is a dedicated device on your home or office network that stores and shares files. Think of it as your own personal cloud. But if your NAS feels sluggish when you stream movies, back up files, or access documents, you need to figure out where the bottleneck is. Testing your NAS speed helps you find out whether the problem is your NAS itself, your local network, or your internet connection.
Most people only think about testing their internet speed with a standard speed test. But your NAS speed depends on a completely different set of factors — your router, Ethernet cables, and drive performance all play a role. Let's walk through exactly how to measure it.
Internet Speed vs. NAS Speed: They're Different Things
Before you start testing, it's important to understand the difference between your internet speed and your NAS transfer speed. They're two separate measurements.
Internet Speed
This is how fast data moves between your home and the wider internet. When you run a broadband speed test, you're measuring the connection between your router and a remote server. A typical home plan might give you 100–500 Mbps download.
NAS Speed (Local Network Speed)
This is how fast data moves between your computer and your NAS within your own network. It never touches the internet. A standard Gigabit Ethernet connection tops out around 940 Mbps in practice, while a 2.5 GbE connection can hit around 2,350 Mbps. If your NAS is connected over Wi-Fi, speeds will be much lower and less consistent.
| Connection Type | Max Theoretical Speed | Typical Real-World Speed | Good For |
|---|---|---|---|
| Gigabit Ethernet (1 GbE) | 1,000 Mbps | 800–940 Mbps | Most home users |
| 2.5 GbE Ethernet | 2,500 Mbps | 2,000–2,350 Mbps | Video editing, large backups |
| 10 GbE Ethernet | 10,000 Mbps | 7,000–9,400 Mbps | Pro workstations, 4K workflows |
| Wi-Fi 6 (802.11ax) | 1,200 Mbps (typical link) | 400–700 Mbps | Casual streaming, light use |
| Wi-Fi 5 (802.11ac) | 866 Mbps (typical link) | 200–450 Mbps | Basic file access |
If your NAS reads and writes are slower than your network connection allows, the bottleneck is probably inside the NAS — its drives, RAID configuration, or processor. If speeds match the network limit, your NAS is performing well and any upgrade means upgrading your network.
4 Ways to Test Your NAS Speed
1. Simple File Copy Test
The easiest method is to copy a large file and time it. Pick a single file that's at least 1 GB — a video file works great. Smaller files give misleading results because overhead eats into the transfer time.
- Map your NAS as a network drive on your computer (SMB or NFS).
- Copy a 1–5 GB file from your computer to the NAS. Note the time.
- Copy the same file back from the NAS to your computer. Note the time.
- Calculate: Speed (MB/s) = File Size (MB) ÷ Time (seconds).
For example, if a 2 GB file (2,048 MB) copies in 20 seconds, that's about 102 MB/s — or roughly 816 Mbps. That's a healthy result on a Gigabit Ethernet connection.
2. Use iperf3 for Raw Network Speed
iperf3 is a free command-line tool that measures pure network throughput between two devices. It strips away disk performance, so you're only testing the network link. Many NAS brands like Synology and QNAP let you install iperf3 through their package managers or via SSH.
- Install iperf3 on your NAS (server) and your computer (client).
- On the NAS, run:
iperf3 -sto start it in server mode. - On your computer, run:
iperf3 -c [NAS-IP-ADDRESS] - The result shows your network throughput in Mbps.
If iperf3 shows 940 Mbps but file copies only hit 500 Mbps, your network is fine — the bottleneck is your NAS drives or file protocol overhead.
3. NAS Built-in Benchmarks
Some NAS operating systems include built-in storage benchmarks. Synology's Storage Manager shows drive health and performance. QNAP offers a similar tool. These test the internal drive read/write speeds independently from the network, which helps you isolate problems.
4. Disk Benchmark Tools (CrystalDiskMark)
On Windows, you can run CrystalDiskMark on a mapped network drive pointing to your NAS. It tests sequential and random read/write speeds. Sequential speeds tell you how fast large file transfers go. Random speeds (often called IOPS — input/output operations per second) tell you how the NAS handles lots of small files, like photo libraries or databases.
Common Bottlenecks and How to Fix Them
Network Issues
The most common problem is a weak link in the network chain. If your router only supports 100 Mbps Fast Ethernet, you'll max out at around 90 Mbps no matter how fast your NAS drives are. Check every link: the NAS port, the Ethernet cable (use Cat 5e or better), and your router's port. One old cable can drag everything down.
If you're connecting over Wi-Fi, expect much lower and less stable speeds. For the best results, always wire your NAS directly to your router with Ethernet. If you're curious about why wireless connections can be unpredictable, check out our guide on how to improve Wi-Fi speed.
Drive Configuration (RAID)
RAID is a way of combining multiple drives for speed, reliability, or both. Different RAID types give different performance results:
- RAID 0 — Fastest reads and writes but no data protection. If one drive fails, you lose everything.
- RAID 1 — Mirrors data across two drives. Read speeds can be faster, but write speeds are about the same as a single drive.
- RAID 5 — Good balance of speed and protection. Needs at least 3 drives. Write speeds are slower than RAID 0 because it calculates parity data.
- SHR (Synology Hybrid RAID) — Similar to RAID 5 in performance but more flexible with mixed drive sizes.
Drive Type
Traditional HDDs (hard disk drives) in a NAS typically read at 150–200 MB/s each. SSDs in a NAS can read at 500+ MB/s. If your network is fast enough (2.5 GbE or 10 GbE), switching to SSDs will make a big difference. On a 1 GbE network, HDDs are usually fast enough since the network is the bottleneck.
Background Tasks
If your NAS is running backups, Plex transcoding, surveillance recording, or disk scrubbing at the same time you're testing, your results will be lower. Run tests when the NAS is idle for the most accurate numbers.
How to Read Your NAS Speed Test Results
Once you've run your tests, here's how to judge if your numbers are normal:
| Setup | Expected Read Speed | Expected Write Speed |
|---|---|---|
| 2-bay NAS, RAID 1, 1 GbE, HDDs | 100–115 MB/s | 90–110 MB/s |
| 4-bay NAS, RAID 5, 1 GbE, HDDs | 110–118 MB/s | 80–110 MB/s |
| 4-bay NAS, RAID 5, 2.5 GbE, HDDs | 250–300 MB/s | 180–250 MB/s |
| 2-bay NAS, RAID 0, 10 GbE, SSDs | 800–1,000 MB/s | 600–900 MB/s |
If your results are significantly below these ranges, start by testing with iperf3 to rule out network issues. If iperf3 looks good, the problem is likely your drives, RAID rebuild status, or an overloaded NAS processor.
Don't Forget to Test Your Internet Connection Too
If you access your NAS remotely — say through Synology QuickConnect, QNAP myQNAPcloud, or a VPN — your experience depends on your internet upload speed. Most home plans offer 10–50 Mbps upload, which means remote NAS access will feel much slower than local access. You can check your current upload speed with our upload speed guide and test to see if your plan is delivering what you're paying for.
Also make sure latency isn't causing problems for remote NAS access. High latency makes file browsing feel laggy even when throughput is decent.
Quick Summary
Testing your NAS speed doesn't require fancy equipment. Start with a simple large file copy to get a baseline number. Use iperf3 to isolate whether the network or the NAS drives are the bottleneck. Make sure you're connected via Ethernet, using Cat 5e cables or better, and that your router supports at least Gigabit speeds. If you're hitting 100+ MB/s on a 1 GbE connection, your NAS is performing well. If not, check your cables, RAID setup, drive health, and background tasks. A few small fixes can often double your transfer speeds.