High Availability with Multipathing

Linux
Audience
Public
Product
FlashBlade
FlashArray
Technology Integrations
Linux
Source Type
Documentation

Path Redundancy Model

Queue-Depth IO Policy

IO Policy Comparison

Policy Behavior Best For
queue-depth Routes to path with lowest queue Mixed workloads (recommended)
round-robin Rotates through paths equally Uniform latency paths
numa Prefers NUMA-local paths NUMA-optimized systems

Enabling Native Multipath

# Add kernel parameter
echo 'options nvme_core multipath=Y' > /etc/modprobe.d/nvme-tcp.conf

# Verify after reboot
cat /sys/module/nvme_core/parameters/multipath
# Output: Y

NVMe-TCP Failover Sequence

NVMe-TCP Failover Parameters

Parameter Default Recommended Description
ctrl-loss-tmo 600s 1800s Time before controller considered lost
reconnect-delay 10s 10s Delay between reconnection attempts
nr_io_queues CPU count - Number of IO queues per controller
Note:

NVMe-TCP uses native NVMe multipathing built into the Linux kernel. This is NOT dm-multipath (multipath.conf, multipathd) - those are for iSCSI/Fibre Channel only.

NVMe-TCP APD (All Paths Down) Behavior

When all paths to an NVMe controller are lost:

  1. ctrl-loss-tmo timer starts - Default 600s (recommended: 1800s for production)

  2. Reconnection attempts - NVMe driver attempts reconnection every reconnect-delay seconds

  3. If timer expires - Controller is removed and I/O fails to application

  4. If path recovers - I/O automatically resumes without intervention