WHAT ARE NETAPP VIRTUAL INTERFACES(VIF)?!

I heard the term and threw me off. So this is me making it easier for myself and for all of you on  what VIF’s are all about.

vQuicky

> VIF = Virtual Interface

> VIF is a feature in Data ONTAP. Data ONTAP is the OS that NETAPP storage devices run on. So basically VIF is a feature of NETAPP storage devices.

> VIFs implement link aggregation – combining multiple network links to work as one.

> Other vendors may call VIFs as Virtual aggregations, link aggregations, trunks and Etherchannels.

> There are three types of VIFs – Single-Mode VIF, Static Multimode VIF and Dynamic multimode VIF.

> VIFs allow you to have higher throughput, fault tolerance and allow no single point of failure to allow HA features for your storage system

inDepth

VIF stands for Virtual Interface which is a feature of your Netapp storage system. The feature allows you to aggregate multiple network interfaces into one logical interface. This allows for a variety of options that now allow higher throughput, fault tolerance and no single point of failure.

Now lets talk about why would you need or use a VIF on your Netapp Storage system. The main bottle neck between compute and storage is the network connectivity between them, among other things.

You may have your Netapp storage equipped with flash cards and SSDs however all that is still throttled because of that 1 GB link you have between your Netapp and your Hypervisor. That means regardless of how fast your random read writes are on your storage system, it is only as good as as that 1GB link. With the VIF you can now aggregate your multiple nics on your Netapp storage system – so that 1 GB link is now looking as a 4GB link by aggregating 4 nics as 1 VIF.

Gets even better – now if you loose one port on that aggregate – no problem! You lost 1 GB bandwidth however you still have 3GB of throughput to your storage system and your virtual machines are still up and no downtime!

You can create VIFS in three different types – single-mode VIF, Static multimode VIF and Dynamic multimode VIF.

In a Single-mode VIF, only one interface is active while others are on standby and ready to take over if the active nic fails. One thing to remember is that all interfaces share a common MAC address. If there are more than one interfaces on stand by in a Single-mode VIF configuration – the storage system picks the interface randomly should the active NIC fail. Since the link failover is monitored and controlled by the storage system, in a Single-mode VIF you DO NOT need a switch that supports link aggregation.

In a Static Multimode VIF all the interfaces in the VIF are active and share a single MAC address. Unlike the Single-mode VIF where only one interface is active at all times, Static multimode VIF has all interfaces communicating at all times. This mode is in compliance with IEEE 802.3ad (static) standard which is the Link aggregation protocol. Any switch that supports aggregates could be used for this mode. The switch here does NOT have to control the packet flow or exchange because that will be taken care of by the storage system and devices on the other end. It is important to remember that the Static Multimode VIF does NOT support IEEE 802.3ad (dynamic) which is also known as Link aggregation control protocol (LACP) or Cisco’s proprietary – Port Aggregation Protocol (PAgP).

In a static multimode VIF the failure tolerance rate is “n-1” where n is the number of interfaces participating in the aggregate. Flow control from transmission perspective is controlled by the NETAPP but it cannot control how inbound frames arrive. That control rests on the devices on the other side of the switch, pressumbly a hypervisor.

Dynamic multimode VIFS can not only detect loss of link status but also loss of data flow as well. This is the most used in high-availability environments. This mode is also in compliance with the IEEE 802.3ad (dynamic) standard which is the Link aggregation control protocol (LACP). However there are some things to remember about Dynamic multimode VIFS.

1. Dynamic multimode VIFS must be connected to a switch that supports LACP

2. The VIFs must be configured as first-level VIFS. First-level VIF is nothing but a trunked interface.

3. They have to be configured to use port based and IP based load balancing methods.

It should be noted that in this mode all interfaces are active and share a single MAC address.

Since we mentioned Load balancing here – it is worth noting that there are three load balancing methods for a multimode VIF. By default when no method is specified, the IP address based load balancing method is used.

The three load balancing methods are, Ip address and Mac address load balancing, Round robin load balancing and Port based load balancing.

Hope this helps 😉 Please comment for any clarifications.