Hi,

i'd like to create a HA-Setup having two nodes. Every offered service
will run in a dedicated VM. Both servers have each two network adapters
combines to a bond. Furthermore i have two switches for not having one
switch as a SPOF. Every slave of the bond should be connected to a
different switch. Live-Migration of the vm's (about 10) should be
possible, and hopefully not to slow.
If possible, i like to increase bandwith AND availibility with the
bond-device.
'Link aggregation - Wikipedia, the free encyclopedia'
(http://en.wikipedia.org/wiki/Link_aggregation) says: "With modes
balance-rr, balance-xor, broadcast and 802.3ad all physical ports in the
link aggregation group must reside on the same logical switch, which in
most scenarios will leave a single point of failure when the physical
switch to which both links are connected goes offline. Modes
active-backup, balance-tlb, and balance-alb can also be set up with two
or more switches."
This is a clear statement.
But the kerneldocumentation
(/usr/src/linux/Documentation/networking/bonding.txt) states something
different:
"11.2.1 HA Bonding Mode Selection for Multiple Switch Topology
-------------------------------------------------------------
In a topology such as the example above, the active-backup and
broadcast modes are the only useful bonding modes when optimizing for
availability; the other modes require all links to terminate on the
same peer for them to behave rationally.

active-backup: This is generally the preferred mode, particularly if
the switches have an ISL and play together well. If the
network configuration is such that one switch is specifically
a backup switch (e.g., has lower capacity, higher cost, etc),
then the primary option can be used to insure that the
preferred link is always used when it is available.

broadcast: This mode is really a special purpose mode, and is suitable
only for very specific needs. For example, if the two
switches are not connected (no ISL), and the networks beyond
them are totally independent. In this case, if it is
necessary for some specific one-way traffic to reach both
independent networks, then the broadcast mode may be
suitable."

alb-balancing and tlb-balancing are not mentioned here. And i think i
don't have an ISL and if i have one, i don't want to use one.
'Cisco Inter-Switch Link - Wikipedia, the free encyclopedia'
(http://en.wikipedia.org/wiki/Cisco_Inter-Switch_Link) says: "... the
use of ISL for new sites is deprecated by Cisco".

Can i use alb-balancing or tlb-balancing for my bond, although the
kernel documentations does not mention it ?
Is alb-balancing or tlb-balancing able to support both ? Increase of
bandwith AND availibility ?

Thanks for any answer.


Bernd


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