Fibre Channel changes management methods
Until standards emerge, vendors are taking unique--and often proprietary--approaches to providing management functionality.
Fibre Channel is a 1Gbps media used to connect high performance storage devices, servers, and workstations. Today, it`s primarily used as the interconnect for storage area networks (SANs). A SAN links one or more servers to multiple storage devices such as disk arrays and tape libraries. Traditionally, these devices were directly connected to individual servers via interfaces such as SCSI, while users accessed them through a server over LANs or WANs. SANs offer users a more flexible environment while improving overall performance and enabling multiple servers to share multiple devices that are up to 10km apart.
Storage management has traditionally assumed that servers or workstations "own" the storage devices and that these devices are locally and directly connected. As such, the interconnect is not a factor in managing the storage devices. Management is between the server and the storage device, dealing only with the methodology of storage and nothing with how the data is moved between devices.
SANs have changed management requirements. Now, users and administrators must be concerned not only with the methodology of storage, but also with how the data gets to the storage devices. SAN devices are no longer co-located with servers. They may be in different buildings, or even across town. In between the server and the storage can be any number of other devices, such as host bus adapters, hubs, switches, and gateways. Since each connecting device can affect the data, all of it must be managed. Once a SAN migrates to long distances and many-to-many connections, it has all the same problems and management requirements as a LAN.
The methods of managing LANs are well known, but Fibre Channel and SANs are new technologies and suppliers are just beginning to look at how to implement management and how to integrate it with LAN management methods. The goal is to make it easy for administrators to simultaneously manage SANs and LANs. To a degree, LAN management methods can be used to manage a SAN.
There are many ways of managing a LAN, but the most common methods use some form of the TCP/IP protocol. These include the simple network management protocol (SNMP), web interfaces such as HTTP/HTML or Java, and command line interfaces (CLI) via protocols like Telnet.
LAN management assumes that devices directly attached to the network support TCP/IP and one or more of the high-level protocols. A SAN is different. It is used mainly for storage, which requires low-latency, low-impact protocols on the Fibre Channel link. Therefore, the basic TCP and management protocol do not come standard with most Fibre Channel devices and have to be added.
Most Fibre Channel devices do not support TCP/IP, although a few host bus adapters (HBAs) do support the protocol. With these HBAs, TCP/IP can be routed onto Fibre Channel without additional software. TCP/IP can flow through any hub or switch and is not affected by the addition of other devices between managed nodes. Unfortunately, TCP/IP HBAs can only talk to other HBAs that support TCP/IP. Hubs, switches, gateways, storage devices, and most HBAs do not support TCP/IP.
Some vendors provide proprietary methods of managing devices over Fibre Channel. Although these methods use the Fibre Channel link, they only provide out-of-band management; that is, the data is not transmitted using standard Fibre Channel signaling. This method works well when two or more of the same vendor`s devices are co-located on the SAN. However, it breaks down when attempting to talk to different vendors` devices, and may not work if two of the same vendor`s devices have to traverse another vendor`s unit (e.g., a hub).
To temporarily work around the issues with in-band management, vendors are adding or using existing Ethernet ports on their devices. These ports, which are implemented with hardware or software management modules, provide a crossover of device management from Fibre Channel to Ethernet. The modules provide an interface into select items of the device and allow the management of the devices.
Using Ethernet, administrators can access devices in familiar methods, often through a GUI interface. This takes advantage of the Ethernet infrastructure--including routers, bridges, gateways, and WAN connections--and allows administrators to manage Fibre Channel devices from anywhere on the network.
There are four main ways the modules can provide information to users:
1. Via a CLI interface to the device using Telnet. This is simple and is readily available from any Windows or Unix workstation, but it relies on administrators knowing the commands for each vendor`s devices. Additionally, Telnet is a polled method, and does not proactively notify administrators of problems.
2. Via industry standard SNMP. This allows the SAN device to act as an agent for an SNMP manager (e.g., Unicenter or OpenView). SNMP uses management information bases (MIBs) to describe the features of a device. However, there are no standard MIBs for Fibre Channel today. Therefore, each vendor offering SNMP must provide a proprietary MIB that can be compiled into the manager. Once compiled, the manager can manage that vendor`s SAN devices, as well as LAN devices. Fibre Channel devices may even offer traps to proactively report critical failures. The proprietary MIBs are today limited to textual representations of the device, and offer limited GUI interfaces.
3. Proprietary GUI. To improve the SNMP interface, some vendors offer their own management software. This software loads on a workstation and uses SNMP to communicate to that vendor`s devices. The software can provide access to all of the vendors` devices on the network and may even provide some level of auto-discovery.
The drawbacks to this method are that each station wanting access to the Fibre Channel devices must first load the software and can only use the software to access that vendor`s devices. This limits the locations where administrators can access the devices and may mean that multiple vendors` software must be loaded.
4. Via an HTTP embedded web server. Once the module provides a web interface, it can be accessed from anywhere on the corporate network. Unique features can be well represented and controlled, and in some cases online help or documentation is available. The embedded web method is the most flexible interface in terms of device access. Unfortunately, the interface requires knowledge of device URLs. This can be compensated for by manually setting bookmarks for all Fibre Channel devices at the most frequently used workstations.
The HTTP method today does not have a method of notifying administrators of critical errors. This has been solved in other Ethernet devices and will soon be available in Fibre Channel modules.
The above methods encompass a variety of vendor-unique methods of management made necessary by a lack of industry standards. Different vendors offer different methods. The industry is aware of the issues and is working on solutions. For example, Fibre Channel organizations are working on proposed standards. And a standards-based RFC on a universal Fibre Channel MIB is being discussed at the Internet Engineering Task Force (IETF) meetings. The MIB will define the types of features that can be managed for each type of device. This will provide a common set of features, while leaving room for proprietary MIBs to manage unique features.
Additionally, the standard MIB will acknowledge web interfaces by providing URL information. Multiple vendors are now working to put together an interoperability demonstration. Once available, the GUI programs can be added to SNMP managers that can handle more than just a single vendor.
The next, and harder, step is providing in-band management--that is, defining a method by which data on the Fibre Channel link carries management information from each device, across all devices in a standard manner. TCP/IP may be one method that could use the above mentioned standards. Other methods may be proposed to use other Fibre Channel protocols. Regardless, the management modules will have to be able to look at the data and determine whether the module is the target. This will require additional hardware, software, and industry standards. As a result, in-band management is most likely a year or more away.
Fibre Channel management has come a long way over the last year, and vendors are working together to further improve it--to at least the level of LANs. Like most things, this will take time.
Management modules enable administrators to access devices in familiar ways. Four methods are illustrated above.
Jeff Freeman is senior director, product management, at Emulex Corp., (www.emulex.com), in Costa Mesa, CA.