Slow I/O Performance when Using iSCSI on RHEL/Rocky/AlmaLinux
KB0023064
Environment
iSCSI on RHEL/Rocky/AlmaLinux
Symptoms
- High latency
- Low throughput
- High await times in
iostat
Cause
- Network congestion
- Single path in use
- I/O scheduler
Resolution
Diagnostic Steps:
# Check I/O wait times
iostat -xz 1
# Check multipath load balancing
multipathd show paths format "%d %T %t %s"
# Network throughput test
iperf3 -c <storage_ip>- Network congestion:
- Enable jumbo frames (MTU 9000)
- Verify flow control settings
- Single path in use:
- Check multipath status
- Verify path policy
- I/O scheduler:
- Use appropriate scheduler for SCSI devices
- Increase queue depth if needed