HP StoreAll Storage Network Best Practices Guide

A BOND modes
Table 20 BOND mode descriptions
Mode DescriptionMode NameMode
Active-backup policy: Only one slave in the bond is active. A different slave becomes
active if, and only if, the active slave fails. The bond's MAC address is externally visible
on only one port (network adapter) to avoid confusing the switch.
active-backup1
In bonding version 2.6.2 or later, when a failover occurs in active-backup mode, bonding
issues one or more gratuitous ARPs on the newly active slave. One gratuitous ARP is issued
for the bonding master interface and each VLAN interface configured above it, provided
that the interface has at least one IP address configured.
Gratuitous ARPs issued for VLAN interfaces are tagged with the appropriate VLAN id.
This mode provides fault tolerance.
Creates aggregation groups that share the same speed and duplex settings. Utilizes all
slaves in the active aggregator according to the 802.3ad specification.
IEEE 802.3ad
Dynamic link
aggregation
4
Slave selection for outgoing traffic is done according to the transmit hash policy; by default
the XOR policy is used. Not all transmit policies may be 802.3ad compliant, particularly
in regards to the packet misordering requirements of section 43.2.4 of the 802.3ad
standard. Differing peer implementations have varying tolerances for noncompliance.
Most switches require some type of configuration to enable 802.3ad mode.
The outgoing traffic is distributed according to the current load (computed relative to the
speed) on each slave.
Adaptive load
balancing
6
The bonding driver intercepts the ARP Replies sent by the local system on their way out
and overwrites the source hardware address with the unique hardware address of one
of the slaves in the bond such that different peers use different hardware addresses for
the server.
Receive traffic from connections created by the server is also balanced. When the local
system sends an ARP Request, the bonding driver copies and saves the peer's IP information
from the ARP packet.
When the ARP Reply arrives from the peer, its hardware address is retrieved and the
bonding driver initiates an ARP reply to this peer assigning it to one of the slaves in the
bond.
A problematic outcome of using ARP negotiation for balancing is that each time that an
ARP request is broadcast it uses the hardware address of the bond. Hence, peers learn
the hardware address of the bond and the balancing of receive traffic collapses to the
current slave. This is handled by sending updates (ARP Replies) to all of the peers with
their individually assigned hardware address such that the traffic is redistributed. Receive
traffic is also redistributed when a new slave is added to the bond and when an inactive
slave is reactivated. The receive load is distributed sequentially (round robin) among the
group of highest speed slaves in the bond.
When a link is reconnected or a new slave joins the bond, the receive traffic is redistributed
among all active slaves in the bond by initiating ARP Replies with the selected MAC
address to each of the clients. The updelay parameter must be set to a value equal or
greater than the switch's forwarding delay so that the ARP Replies sent to the peers will
not be blocked by the switch.
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