SECURING FIBRE CHANNEL FABRICS - Brocade

Chapter 3: SAN Basics for Security ProfessionalsIn some cases, it may be preferable to isolate each fabric from theother. A hybrid implementation can be used in this case by using FCrouting to maintain isolation between the fabrics at each site. Thisallows for the sharing of resources between fabrics while maintainingseparate configuration and management information.Disk Storage and LUNsA LUN is the fundamental unit of disk storage to which the I/O operationsare addressed to. The term LUN is often used to refer to a logical partitionon a disk or group of disks used to build a file system. A LUN can becomposed of an entire disk, a group of disks, or a subset of either.The term LUN is really a misnomer since it actually stands for logicalunit number. The LUN in reality is the specific identifier for a LogicalUnit (LU). The correct term referring to the disk partition is LU, but LUNis used ubiquitously throughout the storage industry and the term LUis very rarely used.Chapter SummaryThe Fibre Channel protocol is in common use in storage area networkstoday. FC frames can carry a payload of 0 to 2,112 bytes-with a maximumframe size of 2,148 bytes. FC devices in the fabric includebackbones, directors, switches, routers, and embedded switches.Hosts, called initiators, connect to devices in the fabric via N_Ports toF_Ports. FC devices connect to each other via E_Ports and EX_Ports.ISL are created by connecting FC switches together and IFLs connectfabrics.FC fabric services improve performance and include path selection viaFSPF, exchange-based routing, and trunking. Frame redirection is aBrocade proprietary technology that allows data to be redirected for aparticular purpose, such as encryption, and then returned.Although there are a number of different fabric topologies, the simplestare not robust enough for most SANs, and so variations of a coreedgeare commonly used. For very large fabrics, multi-tiered fabricsare used for scalability and resilience. Routed fabrics form a metaSAN,which allows devices to communicate without merging to form a singlelarge fabric.Enterprises with multiple data center sites take advantage of extensionusing dark fiber or a long-distance fabric extension solution.SAN storage resides on disk or tape and the terms that describe storageinclude disk-based storage, disk array, LUN(s), and tape-based storage.44 Securing Fibre Channel Fabrics