High Availability with Ksplice

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

iSCSI Path Redundancy Model

Failover Behavior

Failover Diagrams (iSCSI)

Failover behavior diagrams for iSCSI with dm-multipath.

iSCSI/dm-multipath Failover Sequence

Failover Timing

iSCSI Failover Parameters

Parameter Default Recommended Description
replacement_timeout 120s 20s Time before failing over to alternate path
fast_io_fail_tmo 5s 5s Time before marking path as failed
no_path_retry fail queue Behavior when all paths fail
polling_interval 5s 5s Path checking frequency

Configure timeouts in /etc/iscsi/iscsid.conf:

# Aggressive failover (faster, may cause false positives in busy networks)
node.session.timeo.replacement_timeout = 20

# Conservative failover (slower, more tolerant of network glitches)
node.session.timeo.replacement_timeout = 60

Path States

dm-multipath Path Groups

Failback Behavior

Automatic failback (default for active/active arrays):

  • When failed path recovers, I/O is automatically rebalanced

  • No manual intervention required

Manual failback (for active/passive arrays):

# Check current path states
multipathd show paths

# Force path check
multipathd reconfigure

# Manually switch path group
multipathd switchgroup <multipath_device> <group_number>

What is Ksplice?

Ksplice benefits:

  • Zero-downtime kernel updates

  • No reboots required for security patches

  • Maintains iSCSI connections during updates

  • Reduces maintenance windows

  • Improves uptime SLAs

Requires: Oracle Linux Premier Support subscription

Enable Ksplice

Install and configure Ksplice:

# Install uptrack (Ksplice client)
sudo dnf install -y uptrack

# Register with Oracle (requires support subscription)
sudo uptrack-upgrade --register <access_key>

# Enable automatic updates
sudo systemctl enable --now uptrack-upgrade.timer

# Check Ksplice status
sudo uptrack-show

# View available updates
sudo uptrack-upgrade --check

Ksplice Best Practices

  1. Monitor Ksplice updates:

    # Check what patches are applied
sudo uptrack-show

# View update history
sudo uptrack-show --history

# Check for available updates
sudo uptrack-upgrade --check

  2. Schedule updates during low-activity periods:

    # Configure update schedule
sudo systemctl edit uptrack-upgrade.timer

# Add:
[Timer]
OnCalendar=
OnCalendar=Sun 02:00

  3. Test in non-production first:

    • Apply Ksplice updates to dev/test systems first

    • Monitor for any issues

    • Roll out to production after validation

  4. Understand limitations:

    • Some updates still require reboot (rare)

    • Major kernel upgrades require reboot

    • Check uptrack-show for reboot-required updates