HA and bonding - which mode ?

SUSE Product Topics SLES Configure-Administer
1

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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2

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3

Was searching through forums and this thread is almost exactly the same problem that we were looking for an answer to --except we have 4 nics on 2 switches. But unfortunately looks like you never received an answer. Did you ever get your answer of what mode to use to get increased bandwidth and availability?

4

worshamn wrote:
[color=blue]

Was searching through forums and this thread is almost exactly the
same problem that we were looking for an answer to --except we have 4
nics on 2 switches. But unfortunately looks like you never received
an answer. Did you ever get your answer of what mode to use to get
increased bandwidth and availability?[/color]

Have you tried searching the knowledgebase?
http://www.novell.com/support/

I did a quick search for “bonding” and got quite a few hits including
this:

TID 3929220 How To Configure Bonding on Novell Linux products
http://www.novell.com/support/kb/doc.php?id=3929220

–
Kevin Boyle - Knowledge Partner
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5

Hi worshamn,

we’ve decided to go for 802.3ad (AKA “LACP”) for redundant links. Please note that all docs say that this type of bonding must terminate in the same logical switch, which does not necessarily lead to a SPOF: Nowadays switches are prepared for HA, too, you can create a single “logical switch” from multiple hardware switches (be it either stackables on the lower end or an aggregation of multiple modular switches on the higher end of the product lines).

Regards,
Jens

6

On 09/17/2012 08:34 AM, jmozdzen wrote:[color=blue]

Hi worshamn,

we’ve decided to go for 802.3ad (AKA “LACP”) for redundant links.
Please note that all docs say that this type of bonding must terminate
in the same logical switch, which does not necessarily lead to a SPOF:
Nowadays switches are prepared for HA, too, you can create a single
“logical switch” from multiple hardware switches (be it either
stackables on the lower end or an aggregation of multiple modular
switches on the higher end of the product lines).[/color]

Many switches will do Multi-Chassis Link Aggregation (MCLAG or MLAG)… so you
can have your LACP going to different switches as long as they support that.
(which may have been what you were saying)

7

[QUOTE=cjcox;6930]On 09/17/2012 08:34 AM, jmozdzen wrote:[COLOR=blue]

[…][/COLOR]
Many switches will do Multi-Chassis Link Aggregation (MCLAG or MLAG)… so you
can have your LACP going to different switches as long as they support that.
(which may have been what you were saying)[/QUOTE]

yes, MCLAG is one type of implementation I was thinking of - and which I believe to be usually available in the “more expensive routers”.

If you’re on a low budget and need a solution for a small environment, you might use stackable switches, too - some already implement this at a rather low price (but be certain to check the specific type of implementation, some vendors restrict LAGs to a single module!).

Regards,

Jens

8

Thank you for the repsonses, we did end up going with 802.3ad, bonding nics 1 and 2 together and 3 and 4, the 2 groups are on 2 different switches, the switches have been setup to be aware of the aggregation. Then bonding those two bonds together into an active-backup mode.