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The IBM SAN Volume Controller (SVC) is a block storage virtualization appliance that belongs to the IBM System Storage product family. SVC implements an indirection, or "virtualization", layer in a Fibre Channel Storage Area Network (SAN). == Architecture == The IBM 2145 SAN Volume Controller (SVC) is an inline virtualization or "gateway" device. It logically sits between hosts and storage arrays, presenting itself to hosts as the storage provider (target) and presenting itself to storage arrays as one big host (initiator). SVC is physically attached to any available port in one or several SAN fabrics. The virtualization approach allows for non-disruptive replacements of any part in the storage infrastructure, including the SVC devices themselves. It also aims at simplifying compatibility requirements in strongly heterogeneous server and storage landscapes. All advanced functions are therefore implemented in the virtualization layer, which allows switching storage array vendors without impact. Finally, spreading an SVC installation across two or more sites (''stretched clustering'') enables basic disaster protection paired with continuous availability. SVC nodes are always clustered, with a minimum of 2 and a maximum of 8 nodes, and linear scalability. Each I/O group consists of 2 nodes. Each node is a 1U high rack-mounted appliance leveraging IBM System x server hardware, protected by redundant power supplies and an integrated 1U high uninterruptible power supply. Note that the DH8 model is a 2U high unit, with integrated battery backup. An integrated two-row display and five-button keyboard offer stand-alone configuration and monitoring options. Each node has four Fibre Channel ports and two or four 10/1 Gbit/s Ethernet ports used for FCoE, iSCSI and management. All Fibre Channel & FCoE ports on the SVC are both targets and initiators, and are also utilized for inter-cluster communication. This includes maintaining read/write cache integrity, sharing status information, and forwarding reads and writes.〔These ports must be zoned together.〕 Write cache is protected by mirroring within a pair of SVC nodes, called ''I/O group''. Virtualized resources (= storage volumes presented to hosts) are distributed across I/O groups to improve performance. Volumes can also be moved nondisruptively between I/O groups, e.g., when new node pairs are added or older technology is removed. Node pairs are always active, meaning both members accept simultaneous writes for each volume. In addition, all other cluster nodes accept and forward read and write requests which are internally handled by the appropriate I/O group. Path or board failures are compensated by non-disruptive failover within each I/O group. This requires multipath drivers such as IBM Subsystem Device Driver (SDD)〔 or standard MPIO drivers. SVC is based on COMmodity PArts Storage System (''Compass'') architecture, developed at the IBM Almaden Research Center.〔"IBM System Storage SAN Volume Controller", IBM's Redbook SG24-6423-05, pp. 12.〕 The majority of the software has been developed at the IBM Hursley Labs in the UK. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IBM SAN Volume Controller」の詳細全文を読む スポンサード リンク
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