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NetApp disk arrays
Question
How can you set up the redundant network connection for a NetApp array?
Answer
Redundant network connection to a NetApp array can be configured with virtual interface. NetApp provides tree different types of virtual interfaces (VIF):
- Single-mode VIF
- Static Multi-mode VIF
- Dynamic Multi-mode VIF
- Single-mode VIF
A single-mode VIF contains a single active link and a number of links in passive mode. All links in the single-mode VIF share a single MAC address. Only one link is active and sending data therefore there is never a duplicate MAC address on the network. A single-mode VIF is configured with two links connected to redundant switches. Only link e0 is active, while the e1 is in standby mode. If e0 fails (signalled by the link status of the interface going down), the remaining link will take over. In the case of multiple standby interfaces, the storage device will randomly pick one to bring up as the active link. This is commonly known as active passive mode. (Source NetApp Technical report TR3802)
- Static Multi-mode VIF
A static multi-mode VIF contains two or more interfaces in which all links are active. This follows the 802.3ad (static) IEEE standard and requires support and configuration on the switch. However, neither LACP nor PAgP are support in this configuration, so no negotiation or auto-detection of the aggregated ports occurs. The switch must be configured in “on” or “static” mode, which forces the interfaces to form a channel. Static multi-mode VIFs are able to continue operating even if all but one link has been lost. This allows for higher throughput than a single mode VIF, and still provides redundancy. (Source NetApp Technical report TR3802)
- Dynamic Multi-mode VIF
Dynamic multi-mode VIFs are based on Link Aggregation Control Protocol (LACP) as described by the IEEE 802.ad (dynamic) standard. They are similar to static multi-mode VIFs in that they contain two or more active interfaces, share a single MAC address, and require configuration on both ends of the connection. In a dynamic multi-mode VIF, however, additional negotiation parameters are passed between the devices using an LACP Protocol Data Unit (PDU). This allows for the two connected devices to dynamically add and remove links from the channel for reasons other than physical link failure. This is an important distinction, because dynamic multi-mode VIFs can not only detect and compensate for a loss of link, but also a loss of data flow. This leads to higher availability and can help prevent the packet black hole problem discussed in the single-mode VIF section. (Source NetApp Technical report TR3802)
For detailed information and configuration instructions, please see Part 4 IMPROVE PERFORMANCE AND RESILIENCY WITH PORT BONDING of the Technical Report: Ethernet Storage Best Practices, January 2010, TR3802 on www.netapp.com
