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Not Getting 10GbE Speed? 20 Fixes and Solutions

Rob Andrews

20 Ways to Improve Your 10GbE Network Speeds

Upgrading to 10GbE networking should, in theory, allow you to achieve 1GB/s (1000MB/s) network speeds, unlocking ultra-fast data transfers for large files, backups, and high-performance applications. However, many users find that real-world performance falls far short of these expectations. Instead of the seamless, high-speed experience they anticipated, they encounter slower-than-expected speeds, inconsistent performance, and unexplained bottlenecks that limit throughput.

Whether you’re using a NAS, a 10GbE switch, or a direct PC-to-NAS connection, numerous factors can influence network performance. These can range from hardware limitations (such as underpowered CPUs, slow storage, or limited PCIe lanes) to misconfigured network settings (like incorrect MTU sizes, VLAN issues, or outdated drivers). Even the quality of your network cables and transceivers can play a crucial role in determining whether you’re getting the full 10GbE bandwidth or suffering from hidden bottlenecks.

In this guide, we’ll explore TWENTY common reasons why your 10GbE network might not be delivering full speeds, along with detailed fixes and optimizations for each issue. Each point is carefully explained, ensuring that you can identify, diagnose, and resolve the specific problems affecting your network performance. Whether you’re dealing with a NAS that isn’t reaching expected speeds, a 10GbE adapter that’s underperforming, or a switch that isn’t behaving as expected, this guide will help you troubleshoot step by step, so you can fully unlock the potential of your 10GbE network.

1. (Obvious one) Your Storage is Too Slow to Keep Up with 10GbE Speeds

The Problem:

One of the biggest misconceptions about 10GbE networking is that simply having a 10GbE network adapter means you will automatically get 1GB/s speeds. However, your actual storage performance is often the bottleneck. Most traditional hard drives (HDDs) have a sequential read/write speed of only 160-280MB/s, meaning that a single drive cannot fully saturate a 10GbE connection. Even with multiple HDDs in a RAID array, performance may still fall short of 1GB/s due to RAID overhead and the limitations of mechanical disks.

For example, if you have a 4-bay NAS with standard 7200RPM hard drives in RAID 5, you may only reach 500-600MB/s, which is half the potential of your 10GbE network. The situation gets worse if you are using RAID 6, as the additional parity calculations introduce a write performance penalty.

The Fix:

How to Check Disk Speeds:

Run a disk speed test to verify if storage is the issue:

Windows (CrystalDiskMark)

  1. Download and install CrystalDiskMark.
  2. Select your storage volume (NAS drive, local SSD, etc.).
  3. Run a sequential read/write test.
  4. If speeds are below 1GB/s, your storage is the bottleneck.

Linux/macOS (dd Command)

dd if=/dev/zero of=/mnt/testfile bs=1G count=5 oflag=direct

2. Your SSDs or NVMe Drives Are Running at Lower PCIe Speeds

The Problem:

Even if your NAS or PC is using SSDs, you might not be getting full speeds due to PCIe lane limitations. Some NAS devices throttle M.2 NVMe SSDs to PCIe 3.0 x1 or x2, which caps speeds at 800-1600MB/s—not enough to fully saturate a 10GbE connection.

This issue is particularly common in budget-friendly NAS systems and motherboards where multiple M.2 slots share bandwidth with SATA ports or other PCIe devices. Even high-speed SSDs like the Samsung 980 Pro (7000MB/s rated speed) will be bottlenecked if placed in an underpowered slot.

The Fix:

Linux/macOS (Check PCIe Speeds)

lspci -vvv | grep -i nvme

Windows (Check with CrystalDiskInfo)

  1. Download CrystalDiskInfo.
  2. Look for the PCIe link speed in the SSD details.

If speeds are lower than expected, try moving the SSD to a different M.2 slot or checking BIOS settings to enable full PCIe bandwidth.

3. You’re Using DRAM-less SSDs (HMB-Only SSDs Can Throttle Speeds)

The Problem:

Not all SSDs are created equal. Some budget SSDs lack DRAM cache and instead rely on Host Memory Buffer (HMB), which offloads caching duties to system RAM. While this design helps reduce costs, it also means significantly lower sustained write performance.

For a single SSD, this might not be an issue, but in a RAID configuration, the problem worsens as multiple drives compete for system memory. DRAM-less SSDs also tend to overheat faster, leading to thermal throttling, further reducing performance.

The Fix:

4. Your Switch is Not Actually 10GbE (Misleading Switch Descriptions)

The Problem:

Many users unknowingly purchase “10GbE” switches that only have limited 10GbE ports. Some switches advertise 10GbE speeds, but only one or two ports support it, while the rest run at 1GbE.

It’s also possible that your NAS or PC is plugged into a non-10GbE port, creating an invisible bottleneck.

The Fix:

Windows (Check Network Speed)

  1. Open Control Panel > Network and Sharing Center.
  2. Click on your 10GbE adapter → Check Speed (should show 10.0Gbps).

If your switch only has 1-2 ports at 10GbE, you may need to reconfigure your network layout or upgrade to a full 10GbE switch.

5. You’re Using the Wrong Ethernet Cables (Cat5e vs. Cat6/Cat7)

The Problem:

Not all Ethernet cables can handle 10GbE speeds over long distances. If you’re using Cat5e, performance drops significantly after 10 meters.

The Fix:

How to Check Your Cable Type

  1. Look at the cable jacket—it should say Cat6, Cat6a, or Cat7.
  2. If the cable does not specify, assume it’s Cat5e and replace it.

If using fiber, make sure your SFP+ transceivers are rated for 10GbE—many cheap adapters are 1GbE only.

6. Your Network Adapter is Using the Wrong Driver or Firmware

The Problem:

Even if you have a 10GbE network adapter installed, outdated or incorrect drivers can limit speeds or cause inconsistent performance. Many network cards rely on manufacturer-specific drivers for optimal performance, but some operating systems may install generic drivers that lack key optimizations.

This issue is common with Intel, Mellanox, Broadcom, and Aquantia/AQC NICs—especially if they were installed manually or came pre-installed with a NAS or prebuilt server.

The Fix:

  1. Check your network adapter model:
    • Windows: Open Device Manager > Network Adapters and find your 10GbE NIC name.
    • Linux/macOS: Run the following command to list your installed NICs:
      lspci | grep Ethernet
  2. Update the driver manually:
    • Windows: Go to the manufacturer’s website (Intel, Broadcom, Mellanox, etc.) and download the latest driver.
    • Linux: Update using ethtool:
      sudo ethtool -i ethX # Replace ethX with your network interface
  3. Check and update NIC firmware: Some network cards require a firmware update for full 10GbE support. Many Aquantia NICs, for example, need firmware updates to fix link speed negotiation issues.
  4. Ensure your OS isn’t using a generic driver:
    • In Windows, open Device Manager, right-click the NIC, and select Properties > Driver. If it says Microsoft Generic Adapter, update it manually.
    • In Linux, check driver details with:
      ethtool -i ethX

      If the driver is a generic kernel driver, install the manufacturer’s official driver.

7. MTU (Jumbo Frames) is Not Set Correctly

The Problem:

By default, most network devices use a 1500-byte MTU (Maximum Transmission Unit). However, 10GbE networks can benefit from larger packet sizes (9000 bytes, known as Jumbo Frames). If one device has Jumbo Frames enabled but another doesn’t, packets get fragmented, leading to lower speeds, higher latency, and increased CPU usage.

The Fix:

  1. Enable Jumbo Frames (MTU 9000) on All Devices:
    • Windows:
      • Go to Control Panel > Network and Sharing Center > Change Adapter Settings.
      • Right-click your 10GbE adapter, select Properties > Configure > Advanced.
      • Set Jumbo Frame / MTU to 9000.
    • Linux/macOS:
      sudo ifconfig ethX mtu 9000
    • NAS:
      • Synology: Go to Control Panel > Network > Interfaces > Edit and set MTU to 9000.
      • QNAP: Go to Network & Virtual Switch > Interfaces > Jumbo Frames.
  2. Check MTU Settings on Your Switch:
    • If your switch does not support MTU 9000, disable Jumbo Frames or upgrade the switch.
  3. Verify MTU Configuration:
    • Run a ping test with large packets:
      ping -f -l 8972 NAS_IP

      If the packets fragment, MTU isn’t properly configured.

8. Your NAS or PC CPU is Too Weak to Handle 10GbE Traffic

The Problem:

Even if you have fast storage and a 10GbE adapter, a low-power CPU can bottleneck network performance. Many NAS devices use ARM-based or low-end Intel CPUs (e.g., Celeron, Atom, or N-series processors) that struggle to handle high-speed transfers, encryption, or multi-user traffic.

For example, some budget NAS units advertise 10GbE connectivity, but their CPU is too weak to push consistent 1GB/s speeds—especially if multiple users are accessing data simultaneously.

The Fix:

9. VLAN, QoS, or Network Prioritization is Throttling Your 10GbE Traffic

The Problem:

If you’re using a managed switch or router, incorrect VLAN (Virtual LAN) or QoS (Quality of Service) settings may be limiting your 10GbE speeds. Some switches automatically assign lower priority to high-bandwidth devices, throttling performance.

The Fix:

  1. Check VLAN settings:
    • If your 10GbE NAS or PC is in a VLAN with limited bandwidth, remove it from that VLAN or adjust the priority settings.
  2. Disable or Adjust QoS Settings:
    • Log into your switch’s admin panel and look for QoS (Quality of Service) settings.
    • If enabled, check if bandwidth limits are applied to your 10GbE ports.
    • In some switches (e.g., Ubiquiti, Netgear, Cisco), set QoS priority for 10GbE devices to “High”.
  3. Run a Speed Test Without VLAN or QoS:
    • Temporarily disable VLAN/QoS, then test file transfer speeds again.

If speeds improve, your VLAN/QoS settings were throttling your network.

10. Background Processes or Other Network Devices Are Consuming Bandwidth

The Problem:

If you’re not getting full 10GbE speeds, it’s possible that another device is using the NAS at the same time. Even if your PC or NAS seems idle, background tasks like cloud syncing, automated backups, Plex transcoding, or surveillance camera recording can consume CPU, storage I/O, and network bandwidth.

The Fix:

  1. Check if other devices are using the NAS:
    • Windows: Open Task Manager > Network and check if any background processes are consuming bandwidth.
    • Linux/macOS: Use:
      iftop -i ethX
    • On your NAS, check if:
      • Plex or media servers are streaming.
      • Security cameras are recording to the NAS.
      • Backups/snapshots are running in the background.
  2. Pause Background Tasks:
    • Temporarily disable cloud syncing, RAID scrubbing, and backups, then retest network speeds.
  3. Run an IPerf Network Speed Test:
    • Windows/Linux:
      • On NAS:
        iperf3 -s
      • On PC:
        iperf3 -c NAS_IP -P 4
    • If IPerf shows 1GB/s speeds but file transfers don’t, then background processes or storage limitations are the issue.

11. Your SFP+ Transceiver or Media Converter is Bottlenecking Performance

The Problem:

If you’re using SFP+ transceivers or fiber-to-RJ45 media converters, they might not be running at full 10GbE speeds. Many budget-friendly SFP+ modules are actually 1GbE-only or have compatibility issues with certain switches and NICs. Additionally, some fiber-to-copper converters (e.g., cheap third-party models) overheat quickly, leading to throttling and slow speeds.

The Fix:

  1. Check Your SFP+ Transceiver Rating:
    • Run the following command on a Linux-based NAS or switch:
      ethtool ethX
    • If the output shows 1000Mbps instead of 10000Mbps, your SFP+ module is not running at full speed.
  2. Use Verified SFP+ Modules:
    • Stick to brand-certified transceivers (e.g., Intel, Mellanox, Cisco, Ubiquiti, MikroTik).
    • Generic eBay/Amazon SFP+ transceivers may not properly negotiate at 10GbE.
  3. Check for Overheating:
    • Touch the transceiver—if it’s too hot to hold, it may be thermal throttling.
    • Consider active cooling (small heatsinks or airflow near the module).
  4. Verify Media Converters:
    • Some cheap SFP-to-RJ45 converters cap speeds at 5GbE or lower.
    • Try swapping the converter for a direct 10GbE-capable SFP+ transceiver.

12. Your PCIe Slot is Throttling Your 10GbE NIC

The Problem:

Your 10GbE network card (NIC) might be plugged into a PCIe slot that doesn’t provide full bandwidth. Some motherboards limit secondary PCIe slots to x1 or x2 speeds, which reduces network performance significantly.

For example:

The Fix:

  1. Check PCIe Slot Assignment:
    • Windows: Use HWiNFO64 or Device Manager to check PCIe link speed.
    • Linux/macOS: Run:
      lspci -vvv | grep -i ethernet

      If it says PCIe x1, your NIC is bottlenecked.

  2. Move the 10GbE NIC to a Better Slot:
    • Use a PCIe 3.0/4.0 x4 or x8 slot for full bandwidth.
    • Avoid chipset-controlled PCIe slots, as they share bandwidth with SATA, USB, and other devices.
  3. Enable Full PCIe Speed in BIOS:
    • Go to BIOS > Advanced Settings > PCIe Configuration.
    • Set the slot to “Gen 3” or “Gen 4” (depending on your motherboard).

13. SMB or NFS Protocol Overhead is Slowing Transfers

The Problem:

If you’re transferring files over a mapped network drive (SMB/NFS), protocol overhead can reduce real-world speeds. Windows SMB, in particular, can limit large file transfers due to encryption, signing, or buffer settings.

The Fix:

  1. Enable SMB Multichannel for Faster Transfers (Windows):
    • Open PowerShell as Administrator and run:
      powershell
      Set-SmbClientConfiguration -EnableMultiChannel $true
    • This allows multiple TCP connections for higher throughput.
  2. Disable SMB Signing (If Safe to Do So):
    • Windows:
      powershell
      Set-SmbClientConfiguration -RequireSecuritySignature $false
    • Linux:
      Add the following line to /etc/fstab when mounting an SMB share:
      ini
      vers=3.0,seal=no
  3. Try NFS Instead of SMB (If Using Linux/macOS):
    • SMB can be slow for large sequential transfers.
    • NFS performs better for 10GbE direct-attached storage (NAS to PC).
  4. Use iSCSI for Direct Storage Access:
    • If your NAS supports iSCSI, mount an iSCSI target for block-level access, which can be much faster than SMB/NFS.

14. Your Router or Network Switch is Blocking Full Speeds

The Problem:

Many consumer-grade routers and switches have built-in traffic management features that can throttle high-speed connections. Even some high-end managed switches may have bandwidth limits, VLAN misconfigurations, or QoS settings that restrict speeds.

The Fix:

  1. Disable Traffic Shaping or QoS:
    • On a managed switch, log in and disable bandwidth limits on your 10GbE ports.
    • On a router, look for:
      • Smart QoS / Traffic Prioritization (disable it).
      • Bandwidth Limiting (set to unlimited).
  2. Check VLAN Configuration:
    • If your NAS and PC are in different VLANs, traffic might be routed through the main router, slowing speeds.
    • Move both devices into the same VLAN for direct 10GbE connectivity.
  3. Ensure Your Switch Supports Full 10GbE Throughput:
    • Some low-end 10GbE switches have an internal bandwidth cap.
    • Example: A switch with five 10GbE ports but only a 20Gbps internal backplane will throttle performance under heavy load.

15. Windows Power Management is Throttling Your 10GbE Card

The Problem:

Windows Power Management settings may be automatically throttling your 10GbE network adapter to save energy. This can cause inconsistent speeds and unexpected slowdowns.

The Fix:

  1. Disable Energy-Efficient Ethernet (EEE):
    • Open Device Manager → Expand Network Adapters → Right-click your 10GbE adapter → Properties.
    • Under the Advanced tab, find “Energy-Efficient Ethernet” and set it to Disabled.
  2. Set Windows Power Plan to High Performance:
    • Open Control Panel > Power Options.
    • Select High Performance (or Ultimate Performance if available).
  3. Disable CPU Power Throttling:
    • Open PowerShell as Administrator and run:
      powershell
      powercfg -setactive SCHEME_MIN
    • This forces Windows to prioritize performance over power saving.
  4. Check for Interrupt Moderation & Adaptive Inter-Frame Spacing:
    • In Device Manager, under the Advanced tab of your 10GbE adapter, disable:
      • Interrupt Moderation
      • Adaptive Inter-Frame Spacing

16. Your NAS or PC is Routing Traffic Through the Wrong Network (Subnet Mismatch)

The Problem:

Even if you have a direct 10GbE connection between your NAS and PC, your operating system might still route traffic through a slower network interface (e.g., a 1GbE connection or even Wi-Fi). This can happen if your system prioritizes the wrong network adapter, or if your NAS and PC are on different subnets, causing traffic to be routed through a slower router or switch instead of using the direct 10GbE link.

For example:

If your PC is trying to reach the NAS using the 1GbE or Wi-Fi address, it may bypass the 10GbE connection entirely, leading to slow speeds.

The Fix:

  1. Ensure Both Devices Are on the Same Subnet
    • Assign both 10GbE interfaces an IP in the same range (e.g., 192.168.2.x).
    • Set the 1GbE and Wi-Fi interfaces to a different subnet (e.g., 192.168.1.x).
  2. Manually Set the 10GbE Network as the Preferred Route
    • Windows (CMD – Run as Administrator):
      powershell
      netsh interface ipv4 set interface "10GbE Adapter Name" metric=1
    • Linux/macOS:
      sudo ip route add 192.168.2.0/24 dev ethX metric 10
    • A lower metric prioritizes the 10GbE connection over slower networks.
  3. Check Active Routes to Ensure 10GbE is Being Used
    • Windows:
      powershell
      route print
    • Linux/macOS:
      ip route show
    • Look for 192.168.2.x going through the 10GbE adapter. If another network is being used, adjust the routing table.

17. Your SATA Controller is Bottlenecking Multiple Drives

The Problem:

Even if you have fast SSDs or multiple hard drives in RAID, the SATA controller inside your NAS or PC might be the bottleneck. Some budget NAS units and lower-end PC motherboards use cheap SATA controllers (e.g., JMicron, ASMedia, Marvel) that bottleneck total disk throughput.

For example:

The Fix:

  1. Check the SATA Controller in Use:
    • Windows (Device Manager): Expand Storage Controllers and check the SATA controller manufacturer.
    • Linux/macOS:
      lspci | grep SATA
    • If you see JMicron, ASMedia, or Marvel, you might have a bandwidth-limited controller.
  2. Use an HBA (Host Bus Adapter) Instead
    • If your motherboard or NAS has limited SATA bandwidth, install a dedicated LSI/Broadcom HBA card (e.g., LSI 9211-8i, LSI 9300-8i) to get full-speed SATA connectivity.
  3. Check the SATA Backplane in NAS Enclosures
    • Some NAS enclosures have a shared SATA controller for all drives, limiting total speed.
    • If possible, upgrade to a NAS with multiple SATA controllers or use NVMe SSDs instead.

18. Your System’s TCP/IP Stack is Not Optimized for High-Speed Transfers

The Problem:

By default, most operating systems have conservative TCP settings that are optimized for 1GbE networks, but not for high-speed 10GbE connections. Without proper tuning, TCP window size, congestion control, and buffer settings can limit data transfer rates over high-bandwidth connections.

The Fix:

Windows: Optimize TCP Settings via PowerShell

  1. Enable TCP Window Auto-Tuning:
    powershell
    netsh int tcp set global autotuninglevel=normal
  2. Enable Receive Side Scaling (RSS) to Use Multiple CPU Cores:
    powershell
    Set-NetAdapterRss -Name "10GbE Adapter Name" -Enabled $true
  3. Increase TCP Receive Buffers:
    powershell
    netsh int tcp set global rss=enabled
    netsh int tcp set global ecncapability=disabled
    netsh int tcp set global chimney=enabled

Linux/macOS: Increase TCP Buffers

Edit /etc/sysctl.conf and add:

net.core.rmem_max = 67108864
net.core.wmem_max = 67108864
net.ipv4.tcp_rmem = 4096 87380 67108864
net.ipv4.tcp_wmem = 4096 65536 67108864

Then apply the changes:

sudo sysctl -p

19. Antivirus or Firewall Software is Interfering with Network Speeds

The Problem:

Many antivirus and firewall programs scan all incoming and outgoing network traffic, which can significantly slow down 10GbE speeds. Some intrusion prevention systems (IPS), such as those in Sophos, Norton, Bitdefender, and Windows Defender, can introduce latency and CPU overhead when processing large file transfers.

The Fix:

  1. Temporarily Disable Your Antivirus/Firewall and Run a File Transfer Test
    • If speeds improve, your security software is causing the slowdown.
  2. Whitelist Your NAS or 10GbE Connection in Security Software
    • Add your NAS IP address as an exclusion in your antivirus or firewall settings.
  3. Disable Real-Time Scanning for Large File Transfers
    • In Windows Defender:
      • Open Windows Security → Go to Virus & Threat Protection.
      • Under Exclusions, add your NAS drive or network adapter.
  4. Check for Router-Level Security Features
    • Some routers have Deep Packet Inspection (DPI) or Intrusion Prevention (IPS) enabled, which can slow down traffic.
    • Log into your router’s admin panel and disable unnecessary security features for local transfers.

20. Your Network is Experiencing Microburst Congestion (Overloaded Buffers)

The Problem:

Some 10GbE switches have limited packet buffers, causing microburst congestion when multiple devices transfer data simultaneously. This results in random slowdowns, packet loss, and jitter, even if total traffic is well below 10GbE capacity.

The Fix:

  1. Enable Flow Control on Your Switch
    • Log into the switch’s admin panel.
    • Enable 802.3x Flow Control on your 10GbE ports.
  2. Use a Higher-Quality Switch with Larger Buffers
    • Some cheap 10GbE switches have small packet buffers, leading to congestion.
    • Consider an enterprise-grade switch (e.g., Netgear XS716T, Cisco SG550X, Ubiquiti EdgeSwitch).
  3. Monitor Switch Traffic for Spikes
    • Use iftop or Wireshark to monitor packet loss or delays.
    • If needed, upgrade your switch to one with better buffering.

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