2.5 Assembling a Storage Network
Assembling an effective storage network that addresses the needs of an enterprise-class company is difficult. All the devices and software must now be put into production in an effective, manageable solution. This book doesn't describe a complete storage network implementation. Rather, we construct a fictitious storage network that helps illuminate the points made throughout the book.
We call our example Coffee House Inc. Coffee House is a large enterprise with a central data center containing a storage area network and servers for data access. The company also has a production IP network and several data-hungry departments. It is important to realize that the storage networking environment portrayed in the coming paragraphs is not an optimal implementation of storage, but it is the type of network that can be found in the industry. Coffee House does not have a strong background in storage management and has chosen not to invest heavily in storage management resources.
The departments that require large amounts of storage often circumvent the data center and install NAS devices for local storage needs. NAS devices are especially nice for the advertising department, which uses Apple computers rather than the Windows NT and Sun Solaris devices that the rest of the company standardized on. The NAS device in the ad department enables the devices to readily exchange data, whereas the central data center chooses not to "support" the native AppleTalk protocol.
The SAN in the data center uses fibre channel switches to zone particular file-serving hosts to particular block devices on the fabric. Zoning the switches means that the SAN is actually partitioned into separate logical networks. This arrangement is handy for the data center because Windows NT 4.0 tends to span all storage that is visible rather than managing only the storage that is explicitly identified to the server machines. (Later versions of Windows do not have this issue.) The SAN also contains two tape libraries for backup operations. Keeping the tape library on the back-end SAN, rather than on the production network, means that the file servers can back up data without any burden being put on the production network.
Figure 2.1 shows a simplified view of the entire storage network in place at Coffee House Inc. The company administrators must deal with some interesting management issues. For example, how is the data on the inexpensive NAS devices in the advertising department backed up? In years when coffee is not selling well, the IT staff, and perhaps the budget for new storage, will be cut. On the other hand, when coffee is selling well, storage needs will grow exponentially but the IT staff will not expand accordingly (it is hard to find storage and networking experts in a good economy without paying an arm and a leg).
Figure 2.1 Coffee House Inc. storage network
To manage the storage resources in a timely and effective manner, a storage resource manager is necessary, even if the storage network is rearchitected and a new infrastructure is built. The SRM can offer a single point to view the wide array of storage devices in the network. For example, to monitor the health and throughput of the storage network, the SRM can be used to navigate to the switch and then to specific devices attached to the switch for specific volume information. Within the same SRM, it should be possible to monitor and manipulate the health of the NAS devices.
The SRM software must be adaptable to new devices that fit within the Coffee House budget and must be able to manage the devices with policies and automation so as to minimize IT staffing needs. To this end, Coffee House must avoid a situation in which a vendor locks in the company to its hardware, or the SRM requires certain types of hardware or software. This is the exact situation that calls for an SRM created using the Federated Management Architecture.