load balancing in VIF

[Raju Mahala]

Hello Everybody,

Can anybody describe what algorithm is applied in ONTAP for load
balancing across the network ports in a multi type vif. Mode is IP
load balancing.

I feel it dedicate particular IPs to one of the network port so all I/
O transfer with that IP is done with a specific network port. Am I
right ?

-Raju

[Ganesan Sudalai]

Hi Raju,

Herewith i am trying to give you a little insight into Single mode and Multimode as you were asking some questions earlier on this too

Virtual Interfaces (VIF) 
VIFs, also known as port channeling, allow for high availability network configurations on Netapp filers. VIFs can be configured as either single-mode or multi-mode.

A filer can have multiple VIFs configured.

 * Single-mode VIFs
Single-mode VIFs allow for failover across network switches. A single-mode VIF should be used to provide redundancy with switch connections. Single-mode VIFs can contain two multi-mode VIFs to allow for increased network bandwidth on a given ip segment. When a single-mode VIF is brought online, one of the two interfaces (or multi-mode VIFs) is favored. This preferred interface can be specified by the filer administrator.

 * Multi-mode VIFs
Multi-mode VIFs are used with port channeling (or Cisco Etherchannel) configurations. A Netapp filer allows up to 16 Gigabit Ethernet ports to be channeled together. A multi-mode VIF should be used to provide increased network throughput for data access. Multi-mode VIFs provide load balancing of outgoing traffic from the filer. The filer supports the following load-balancing methods: IP-address based, MAC-address based, or Round Robin. 

When determining the number of interfaces to include in a multi-mode VIF, the filer administrator must understand the network load that will be applied to the filer on a given ip segment. Most mtuli-mode VIFs contain 2 - 3 network interfaces. 
                
The individual interfaces in a multi-mode VIF can be separated across multiple network switch blades to provide redundancy. If a single interface in a multi-mode VIF fails, the VIF continues to send traffic on the remaining interface(s).
                
More on Multimode load balancing

IP-address and MAC-address based

In both of these methods, the last byte of the source and destination address (IP address and MAC address) is used to determine the interface to use for the outgoing frame. The following formula is used:

((source_address XOR destination_address) % number_of_links)

If the result of this formula maps to an interface that is not in the UP link-state, the next active interface is used.

For example, a vif consisting of eight physical interfaces is created with the IP address-based load-balancing method. It is configured with IP address 10.0.0.10. Based on the above formula, an IP frame going through this vif to the destination IP address 172.26.15.224 will use interface #2, provided that this interface is in the UP link-state.

Note
Do not select the MAC-address based load-balancing method when creating vifs on a filer that connects directly to a router. In such a setup, for every outgoing IP frame, the destination MAC address will be the MAC address of the router. As a result, only one interface of the vif will be used.

Round robin:

Unlike the IP-address and MAC-address load-balancing methods, this method provides true load balancing. This method may cause out-of-order packet delivery and retransmissions due to overruns.

This method of load balancing is recommended for clients connected in a back-to-back configuration with a filer.

Lemme know if you have further specific questions

--
Cheers

Ganesh

One day can't change a person, but one person can change a day !!!
~ Dr. Napoleon Hill

http://poigaiblog.blogspot.com/

[Raju Mahala]

Hi Ganesh,

thanks yaar, you didn't left much to ask. But anyway I couldn't
understand the formula you mentioned.
in your ex. how you are getting #2
10 XOR 224 % 8 how it is 2

thanks for describing it little bit

- Raju

> ((*source_address* XOR *destination_address*) % *number_of_links*)

>
> If the result of this formula maps to an interface that is not in the UP
> link-state, the next active interface is used.
>
> For example, a vif consisting of eight physical interfaces is created with
> the IP address-based load-balancing method. It is configured with IP address
> 10.0.0.10. Based on the above formula, an IP frame going through this vif to
> the destination IP address 172.26.15.224 will use interface #2, provided
> that this interface is in the UP link-state.
>

> *Note*

> Do not select the MAC-address based load-balancing method when creating vifs
> on a filer that connects directly to a router. In such a setup, for every
> outgoing IP frame, the destination MAC address will be the MAC address of
> the router. As a result, only one interface of the vif will be used.
> Round robin:
>
> Unlike the IP-address and MAC-address load-balancing methods, this method
> provides true load balancing. This method may cause out-of-order packet
> delivery and retransmissions due to overruns.
>
> This method of load balancing is recommended for clients connected in a
> back-to-back configuration with a filer.
>
> Lemme know if you have further specific questions
>

> On 2/21/07, Raju Mahala <rajumah...@gmail.com> wrote:
>
>
>
>
>
>
>
> > Hello Everybody,
>
> > Can anybody describe what algorithm is applied in ONTAP for load
> > balancing across the network ports in a multi type vif. Mode is IP
> > load balancing.
>
> > I feel it dedicate particular IPs to one of the network port so all I/
> > O transfer with that IP is done with a specific network port. Am I
> > right ?
>
> > -Raju
>
> --
> Cheers
>
> Ganesh
>
> One day can't change a person, but one person can change a day !!!
> ~ Dr. Napoleon Hill
>

> http://poigaiblog.blogspot.com/- Hide quoted text -
>
> - Show quoted text -

[Raju Mahala]

On Feb 22, 9:42 pm, "Raju Mahala" <rajumah...@gmail.com> wrote:
> Hi Ganesh,
>
> thanks yaar, you didn't left much to ask. But anyway I couldn't
> understand the formula you mentioned.
> in your ex. how you are getting #2
> 10 XOR 224 % 8 how it is 2
>
> thanks for describing it little bit
>
> - Raju

Hi Ganesh,

What is this sign - %
Earlier I thought it is division thats why I was getting wrong answer.
But if it is modulo then its ok.
Is it modulo ?

- Raju

[Raju Mahala]

One another query. From where it counts network link. From zero or 1.
So what if modulo comes zero.

-Raju

[Raju Mahala]

> -Raju- Hide quoted text -

>
> - Show quoted text -

Sorry Ganesh things are coming one by one not in one shot.

Can you suggest that which load balance should use at Near Liner
storage (R200) which we are using for snapvault. Because it don't have
many clients to communicate so "IP load balance" would balance out the
trafic or we should use round robin.

- Raju

[Ganesan Sudalai]

Raju,

I am planning to reply all of your queries at once.

"IP Addr or Mac Addr"  load balancing depends on the Destination clients mostly.
% symbol nothing but "modulo" i assume, So It depends how many interfaces you have.
So the Out IO is sent according to the no of Interfaces configured in the VIF.
However i had never worked out b4 u did :-p (Shame, Shame)

Network Link - I assume it starts from 0

Again Look at the Info i provided. I Round robin just forwards the IO one by one interface.
You can only go for IP Load Balancing when you have many clients in different NW segment spread across
with diff IP Range. But here you need to do at ur risk because you need to understand the network
thoroughly to recommend this. However i have read somewhere that you need to keep check if it is
going to be "out of order packets" / No of Retransmission after implementing this to see how your load balancing is
utilized in your environment.

Hope this answers your queries.

--
Cheers

Ganesh

One day can't change a person, but one person can change a day !!!

http://poigaiblog.blogspot.com/

[Ganesan Sudalai]

Here are the commands on how you can monitor VIF's

if stat [VIF_name] [interval ] - Displays the number of packets received and transmitted on each link that makes up the virtual interface.
vif status [VIF_name] - Displays the status of the specified virtual interface. This includes vif specific information, uptime, configuration, number of packets and bytes, etc. 

Other commands that are useful for looking for errors are as follows:

ifstat [VIF_name]

This displays statistics about packets sent and received and network interfaces and is useful in determining total usage of all network interfaces within a VIF. This reports overall network information, however, it must be known which interfaces belong to each vif.

netstat -i

This shows the state of interfaces which have been configured.

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