HP StorageWorks 2/24 FW 07.00.00/HAFM SW 08.06.00 McDATA Products in a SAN Env - Page 163
Router Name Servers, server database.
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Implementing SAN Internetworking Solutions 4 During SAN router configuration, each R_Port is assigned (through the SANvergence manager application) a unique Fabric_ID between 1 and 12. Although the theoretical limit is 12 Fabric_IDs per mSAN, the supported limit is six. As shown in Table 4-1, four Area_IDs are available to each Fabric_ID. Therefore, the combination of domain, area, and fabric IDs creates a theoretical limit of 1,024 devices per fabric (although the supported number is far less). When a fabric element encounters a device with a Fibre Channel network address starting with Domain_ID 30 or 7E, the associated device is physically connected to a different fabric. In addition, routing communication between the fabric element and device is provided through FC_NAT technology. Fibre Channel network addresses are not unique to each routed fabric (and require router translation for cross-fabric communication) because the Domain_ID space is reused across fabrics. Although device network addresses are router translated, device WWNs are not translated and remain consistent across the entire routed fabric. Router Name Servers Each SAN router in an mSAN (up to two) maintains an mSNS database. With one SAN router installed, the router maintains a primary simple name server (pSNS) database with information about all fabric-attached or router-attached devices in the mSAN (and across iSANs). The pSNS, using the router fabric manager R_Port as a conduit, interfaces with the fabric SNS to form a complete name server database. With two SAN routers installed, one router maintains a pSNS database and the second router maintains a secondary simple name server (sSNS) database. Each mSAN always has one pSNS. The sSNS contains information only about devices directly attached to the second router and is a client to the pSNS. The pSNS router is userselected or assigned during the build fabric process on the basis of the lowest WWN. The secondary router sSNS transmits connectivity information to the primary router pSNS as required. Because SNS databases use unicast and subnet broadcasts to communicate, the pSNS and sSNS routers must be configured on the same subnet. If the mFCP IRL between the routers segments, different information exists in the SNS databases. Implementing SAN Internetworking Solutions 4-19