Data Domain - Troubleshooting Network Frame errors

This article describes how to troubleshoot network frame errors on the Data Domain.
 

eth4c Link encap:Ethernet  HWaddr x:C7:AA:x:12:7E  
          inet addr:x.x.x.7  Bcast:x.x.x.x  Mask:255.255.254.0
          inet6 addr: fe80::f6c7:aaff:fe58:127e/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:115362856103 errors:0 dropped:2939814 overruns:10098 frame:79198392
          TX packets:29061855128 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:167162598519873 (152.0 TiB)  TX bytes:25775705362014 (23.4 TiB)
          Interrupt:47 Memory:b4020000-b403ffff 

Framing errors can come from various factors that often indicate potential hardware or compatibility issues. Some common causes include:

1. Compatibility issue between the two transceivers although this can also show as lower speed selection when using autoneg.
2. Synchronization issues, related to number 1, but it can occur between compatible transceivers.
3. Wrong cable type. For example, using an InfiniBand cable instead of a standard, supported Ethernet cable.
4. A bad cable
5. A bad connector on the Data Domain or on the switch.
6. The hardware transceiver on the Data Domain or the switch is bad.
7. The hardware transceiver is the wrong kind or is not supported.
8. For copper, external signals can cause noise on the line and cause framing errors.

Go through the eight items listed above to see if any of these items contribute to the issue.
Open a case with Data Domain support for more troubleshooting if none of these items resolve this issue.

Check for frame errors in the previous auto support and historically with elysium.

1. Frame errors indicate a faulty component such as a bad cable or small form-factor pluggable transceivers. 
2. If there are thousands of frame errors and the interface is Fiber, it can be a bad transceiver on the dd side, a bad optical cable, or a bad transceiver on the customer switch side.
3. The customer is responsible for replacing cables and transceivers on their side. 
4. If the interface is intermittent or down and there are frame errors, the components must be replaced. 
5. Frame errors also contribute to slow performance since packets must be retransmitted multiple times. 
6. The net show configuration section of the auto support shows the interface statistics example below with an interface with many frame errors. 
         
   The command to list the interface statistics in the CLI is:

   # net show config 

How Frame Errors Impact Data Domain Performance

Frame errors on a network interface indicate corrupted Ethernet frames—often caused by bad cabling, duplex mismatches, or physical layer issues. These errors force the network stack to drop and retransmit packets, which has a cascading effect on the Data Domain system:

1. Increased Retransmissions

• Every corrupted frame means that the sender must resend data.
• For Data Domain, replication and backup traffic are heavy and continuous. Retransmissions multiply the workload because:
  • The same data segments are read from disk again.
  • Compression and deduplication logic re-run for retransmitted chunks.

2. Higher CPU and Memory Utilization

• Data Domain uses CPU-intensive processes for:
  • Deduplication (fingerprinting segments)
  • Compression
  • Encryption (if enabled)
• When frames fail and data is resent, these processes repeat unnecessarily, consuming extra CPU cycles and memory.

3. Filesystem Strain

• The DD filesystem (DDFS) is optimized for sequential writes and segment lookups.
• Retransmissions cause non-sequential I/O patterns, forcing the filesystem to:
  • Re-read segments.
  • Recalculate hashes.
  • Maintain consistency for partially completed writes.
• This leads to extra disk seeks and cache pressure, slowing down overall throughput.

4. Backup Duration Increases

• Because the effective network throughput drops (due to re-transmits and errors), backups take much longer.
• The DD system feels taxed because:
  • It is doing more work per unit of data delivered.
  • Network stalls cause pipeline inefficiencies; threads wait for data, increasing latency.

Bottom Line

Frame errors create a vicious cycle:

• Bad frames → retransmissions → repeated dedup/compression → extra disk I/O → CPU strain → slower backups.

Recommended Fix

• Check physical network health:
  • Replace faulty cables.
  • Verify Network Interface Card (NIC) speed or duplex settings.
  • Monitor switch port errors.
• Ensure MTU settings match across the path.
• If errors persist, consider NIC or switch hardware issues.