How to Fix Slow UGREEN NAS Transfer Speeds

A 100Mbps connection normally transfers a large file at roughly 10 to 12 MB/s. A 1GbE connection delivers roughly 125 MB/s, while 2.5GbE can reach approximately 312.5 MB/s under suitable conditions. A 10GbE connection has a 1250 MB/s theoretical ceiling.

Actual transfer speed is set by the slowest component in the network and storage path:

• NAS network port
• Computer network adapter
• Router or switch port
• Ethernet cable
• USB dock or Ethernet adapter
• Client storage
• NAS storage pool
• Transfer protocol

Run a Controlled Local Transfer Test

Use this baseline:

1. Connect both the UGREEN NAS and computer through Ethernet.
2. Keep both devices on the same local network, preferably connected to the same switch.
3. Disable any VPN running on the computer.
4. Connect through the NAS local IP address instead of UGREENlink or another remote-access route.
5. Use one file larger than 5GB. Avoid folders containing thousands of small files for the first test.
6. Copy the file from a client SSD to the NAS.
7. Copy the same file from the NAS back to the client SSD.
8. Pause cloud synchronization, media indexing, downloads, and other removable workloads.
9. If RAID rebuilding, storage synchronization, or Data Organizing is active, record that condition and repeat the benchmark after it finishes.
10. Open Task Manager in UGOS Pro and watch network, hard-drive, and storage-space activity during both transfers.

On Windows, access the test share with a local path such as:

\\192.168.1.100\Shared-folder

On macOS, open Finder, select Go > Connect to Server, and enter:

smb://192.168.1.100/Shared-folder

Replace the example address and folder name with those used by your NAS.

The two transfer directions measure different operations:

Task Manager helps separate the network from the storage pool:

For separate network-only and storage-only benchmarks, follow our guide to testing UGREEN NAS read and write speed.

If Speed Stays Around 10 to 14 MB/s

A stable result in this range strongly suggests that one part of the path is running at 100Mbps.

In UGOS Pro, open Control Panel > Network > Network Connections and inspect the negotiated speed of the active LAN interface.

Then check the computer’s network status. A 2.5GbE NAS connected to a computer negotiating at 100Mbps will still transfer at approximately 10 to 12 MB/s.

Check the path in this order:

1. Confirm which NAS LAN port is carrying the transfer.
2. Check the negotiated speed on the computer.
3. Confirm that the router or switch port supports Gigabit Ethernet or faster.
4. Replace the Ethernet cable with a known-good Cat6 or better cable.
5. Move the cable to another switch or router port.
6. Bypass a USB dock or adapter and test with a known-good Ethernet connection.
7. Restart the affected switch port, adapter, or client after changing the cable.

Also open Control Panel > Network Settings > Traffic Control. Review any rule applied to SMB or all services. A rate-limit rule can hold the transfer below the negotiated network speed even when every cable and port is working correctly.

Resolve the 100Mbps network link before changing RAID settings or installing an SSD cache.

If Speed Stays Around 90 to 110 MB/s

A stable large-file transfer around 100 to 110 MB/s is normal for a 1GbE path.

If your UGREEN NAS has 2.5GbE or 10GbE, inspect the rest of the connection:

• Does the computer have a matching network adapter?
• Does the switch support that speed on both ports?
• Is the computer connected through a 1GbE USB dock?
• Is the NAS being accessed through the IP address assigned to a slower interface?
• Is one part of a mesh router or switch uplink limited to 1GbE?

When a NAS has multiple network interfaces, use the local IP address assigned to the intended high-speed port for the controlled test.

A normal SMB file copy uses one link. Link aggregation distributes separate connections and adds redundancy. SMB Multichannel can use multiple suitable links for one workload when both endpoints support and configure the feature correctly. Microsoft explains the requirements for SMB Multichannel.

When Upload and Download Speeds Are Different

A computer-to-NAS transfer is often described as an upload. It reads from the computer’s drive and writes to the NAS storage pool.

A NAS-to-computer transfer reads from the NAS and writes to the computer’s drive. Different speeds in the two directions help identify which storage operation is limiting the result.

For example:

• Fast NAS reads with slower NAS writes can point to the RAID write path, parity calculation, or sustained write speed of the drives.
• Slow transfers from the computer can originate from a slow source HDD even when the NAS is ready to receive data faster.
• Fast uploads followed by slow downloads can indicate that the client destination drive is the limit.
• High CPU usage in only one direction can point to SMB signing, encryption, antivirus scanning, or another client-side process.

Repeat both directions with the same large file. Changing the file, client, and transfer direction simultaneously introduces too many variables.

Why Small Files Transfer More Slowly

One 20GB video and 20GB distributed across 200,000 documents contain the same amount of data, but they do not create the same workload.

Each small file requires additional operations:

• Create or open the file
• Check permissions
• Read and update metadata
• Create directory entries
• Close the file
• Confirm the operation over the network

These operations reduce the reported MB/s even when the network is healthy.

For a one-time migration, placing a large group of small files into an archive before transferring it reduces the number of separate file operations. Make sure the source and destination have enough free capacity for the archive and extracted files.

For folders that change regularly, a synchronization task is more efficient than copying the entire folder again because it transfers only new or changed data.

SSD cache helps repeated access to hot data and offers little benefit during a one-time sequential copy. A compatible SSD storage pool is more useful for workloads that repeatedly access large numbers of small files, databases, virtual machines, or application data.

When the Network Is Fast but SMB Is Slow

If a network-only test reaches the expected speed but an SMB file copy does not, inspect the protocol and both endpoint devices.

On UGREEN NAS, open Control Panel > File Services > SMB. Use SMB 2 or SMB 3 for current computers.

Other checks include:

• Test the same file from a second wired computer.
• Confirm that the client source or destination drive is fast enough.
• Check whether antivirus or endpoint-security software scans every transferred file.
• Review SMB encryption settings if the CPU becomes saturated.
• Confirm that the client is connecting to the intended local NAS address.
• Disconnect stale mapped connections that point to another NAS IP address.

Our SMB and NFS file-sharing guide covers protocol selection and shared-folder access in more detail.

When Speed Starts Fast and Then Drops

A transfer that begins quickly and then settles at a lower speed is often showing the difference between cached performance and sustained performance.

The initial data may be accepted by memory, an SSD cache, or the client operating system. Once that temporary buffer fills, the transfer falls to the sustained speed of the storage path.

Check Task Manager while the decline happens:

• High drive or storage-space activity indicates that the storage pool is processing data as fast as it can.
• High CPU usage points toward protocol processing, applications, compression, encryption, or parity work.
• Low network utilization with high storage utilization indicates a storage ceiling.
• A sudden drop on an NVMe pool can indicate thermal throttling. Check SSD temperature and cooling.

Storage-pool activity also matters. RAID rebuilding, RAID synchronization, Data Organizing, media indexing, backup tasks, and multiple active applications compete for the same drives.

Many current NAS-rated HDDs publish maximum sustained sequential rates around 200 to 260 MB/s per drive. A four-drive RAID 5 stores three data blocks and one parity block per stripe, giving it a rough pre-overhead sequential ceiling of 600 to 780 MB/s. Parity calculation, filesystem overhead, drive model, pool activity, and the client reduce real write throughput.

A single HDD or two-drive HDD RAID 1 pool cannot saturate a 10GbE connection. RAID 5 and other multi-drive arrays aggregate drive throughput, while SSD pools provide the higher IOPS and lower latency required by more demanding workloads.

If controlled tests confirm that your current network port, bay count, or storage configuration is the permanent performance ceiling, browse and filter UGREEN NAS storage by networking and storage configuration.

If the slowdown appears during RAID work, use our guide to slow NAS performance during RAID synchronization.

A delay only on the first access can come from drive hibernation. Spinning HDDs need several seconds to wake. Once awake, subsequent transfers should return to their normal sustained speed.

If the storage pool is nearly full, free capacity before evaluating performance. Filesystem, RAID type, fragmentation, snapshots, and write pattern all affect how a heavily used pool behaves, so one universal fullness percentage would be misleading.

When Transfers Stall or Disconnect

Intermittent transfers require a different check from consistently low throughput.

Start with MTU. The standard Ethernet MTU is 1500, and it is the safest diagnostic baseline.

In Control Panel > Network Settings > Network Connections, edit the active interface and check its MTU. Set the NAS, client, and relevant network equipment to 1500 while troubleshooting.

Only test jumbo frames after the standard configuration is stable and every part of the path supports the same larger MTU. A NAS set to 9000 with a client, switch, dock, or adapter still using 1500 can produce transfers that start, stall, or fail.

Then check:

• Loose or damaged Ethernet cables
• A failing switch or router port
• Unstable USB Ethernet adapters
• Docking-station firmware
• Client sleep and network power-saving settings
• Duplicate IP addresses
• A network route switching between wired and wireless interfaces

Change one setting or component at a time and repeat the same large-file test. Record the working IP, gateway, DNS, bond, bridge, and MTU configuration before resetting network settings.

Wi-Fi, Cloud, Remote Access, and Thunderbolt Need Different Tests

The practical speed table at the beginning applies to controlled wired local transfers. Other connection paths introduce different limits.

Evaluate cloud, remote, Wi-Fi, and Thunderbolt transfers against the limits of their respective connection paths.

What to Record Before Contacting Support

If the controlled local transfer remains slow, record the complete test path before contacting UGREEN Support:

• UGREEN NAS model
• UGOS Pro version
• Computer operating system
• NAS negotiated link speed
• Computer negotiated link speed
• Router or switch model
• USB dock or Ethernet adapter model
• Ethernet cable category
• Local NAS IP address used for the test
• Transfer protocol
• Test-file size
• Computer-to-NAS speed
• NAS-to-computer speed
• Task Manager CPU, network, drive, and storage-space activity
• Storage-pool status
• RAID type
• Active backup, synchronization, indexing, or storage tasks
• Whether the problem affects one client or every client

Screenshots of Network Connections, Traffic Control, Task Manager, and the transfer window preserve the evidence that matters. With those results, the bottleneck can be investigated as a specific network, protocol, client, or storage problem instead of a general report that the NAS feels slow.