10.1 IP Storage Networking Expands Remote Data Replication

The distance and performance limitations of Fibre Channel switches primarily are the result of practical rather than technological barriers. As mentioned in Chapter 9, "Assessing Network Connectivity," virtually all of the world's private and public networks now use IP as their communications protocol, so all other protocols, including Fibre Channel, must be converted to or encapsulated in IP packets for transmission across standard IP networks. Beyond that, conventional Fibre Channel switches typically have none of the wide-area networking facilities that are common in IP switches, such as large data transmission buffers, intelligent credit spoofing, and data compression, which collectively improve long-distance network performance.

Some of the new multiprotocol storage switches include all of those wide-area IP networking facilities and provide wire-speed protocol conversion between Fibre Channel and IP. Therefore, they can be used to front-end existing Fibre Channel switches or Fibre Channel end systems and link them via standard IP networks to remote locations that can be hundreds or even thousands of miles away.

With large data transmission buffers and intelligent credit spoofing, the multiprotocol switches can convince the Fibre Channel switches or end systems to forward chunks of data much larger than the amount that could be stored in their own buffers. The multiprotocol switches continue to issue credits until their own buffers are full, while the originating Fibre Channel devices suppose that the credits arrived from the remote site. Credit spoofing affects only the flow rate of the data and not the data itself or its end-to-end write-complete acknowledgments, so the integrity of the data never is compromised.

The added reach and performance of IP storage networking gives IT professionals more options for backup and consolidation. Data centers can back up each other, or a centralized backup data center can be established and shared among the primary data centers, as shown in Figure 10-1.

Figure 10-1. Remote data replication and centralized backup with IP storage switches.

Since storage data can be moved faster and farther over economical high-speed networks, it now is possible to back up more applications at greater distances from the areas that might be impacted by an earthquake or hurricane . During off-peak periods, the storage network can be used to transfer data to archival sites, where it can be copied to optical disks or tapes. Compared to physically transporting the media, storage networking offers a less labor- intensive , more secure, and more reliable approach. Centralizing the media transfer also may be more economical, as many sites can share the backup equipment and staff.