Grid Storage

Definition: Grid storage, analogous to grid computing, is a new model for deploying and managing storage distributed across multiple systems and networks, making efficient use of available storage capacity without requiring a large, centralized switching system.

A grid is, in fact, a meshed network in which no single centralized switch or hub controls routing. Grids offer almost unlimited scalability in size and performance because they aren't constrained by the need for ever-larger central switches. Grid networks thus reduce component costs and produce a reliable and resilient structure.

Applying the grid concept to a computer network lets us harness available but unused resources by dynamically allocating and deallocating capacity, bandwidth and processing among numerous distributed computers. A computing grid can span locations, organizations, machine architectures and software boundaries, offering power, collaboration and information access to connected users. Universities and research facilities are using grids to build what amounts to supercomputer capability from PCs, Macintoshes and Linux boxes.

After grid computing came into being, it was only a matter of time before a similar model would emerge for making use of distributed data storage. Most storage networks are built in star configurations, where all servers and storage devices are connected to a single central switch. In contrast, grid topology is built with a network of interconnected smaller switches that can scale as bandwidth increases and continue to deliver improved reliability and higher performance and connectivity.

What Is Grid Storage?

Based on current and proposed products, it appears that a grid storage system should include the following:

Modular storage arrays: These systems are connected across a storage network using serial ATA disks. The systems can be block-oriented storage arrays or network-attached storage gateways and servers.

Common virtualization layer: Storage must be organized as a single logical pool of resources available to users.

Data redundancy and availability: Multiple copies of data should exist across nodes in the grid, creating redundant data access and availability in case of a component failure.

Common management: A single level of management across all nodes should cover the areas of data security, mobility and migration, capacity on demand, and provisioning.

Simplified platform/management architecture: Because common management is so important, the tasks involved in administration should be organized in modular fashion, allowing the autodiscovery of new nodes in the grid and automating volume and file management.

Three Basic Benefits

Applying grid topology to a storage network provides several benefits, including the following:

Reliability. A well-designed grid network is extremely resilient. Rather than providing just two paths between any two nodes, the grid offers multiple paths between each storage node. This makes it easy to service and replace components in case of failure, with minimal impact on system availability or downtime.

Performance. The same factors that lead to reliability also can improve performance. Not requiring a centralized switch with many ports eliminates a potential performance bottleneck, and applying load-balancing techniques to the multiple paths available offers consistent performance for the entire network.

Scalability. It's easy to expand a grid network using inexpensive switches with low port counts to accommodate additional servers for increased performance, bandwidth and capacity. In essence, grid storage is a way to scale out rather than up, using relatively inexpensive storage building blocks.

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網格存儲

定義：網格存儲與網格計算類似，是部署和管理分布在多個系統和網絡上的存儲的新模式，在無需集中式大型交換系統的情況下，高效地利用可資使用的存儲容量。

網格實際上是一個網狀網絡，其中沒有控制路由的單個集中式交換機或集線器。網格在規模和性能上提供了無限的擴展性，因為它們不會受越來越大的集中式中央交換機這個需求的束縛。因此，網格網絡降低了構件的成本，生成一個可靠且有彈性的結構。

將網格概念應用于計算機網絡，讓我們通過動態分配和重新分配數量眾多的分布式計算機的容量、帶寬和處理能力，利用可用但未用的資源。計算網格可以跨越地域、機構、機器架構和軟件界限，給連接著的用戶提供處理能力、協作和信息存取。大學和研究機構正在利用網格提供 PC機、蘋果機和Linux機組成的、可與巨型機匹敵的計算能力。

有了網格計算之后，出現利用分布數據存儲的類似模型只是個時間問題。大多數存儲網絡是星型結構，其中所有服務器和存儲設備都與單一的中央交換機相連。相反，網格的拓撲結構是互聯在一起的小服務器網絡，可以隨著帶寬的增加而增加服務器，繼續提供更好的可靠性和更高的性能及連接性。

何為網格存儲?

基于目前已有的和建議中的產品，網格存儲系統應該包括下列組成部分：

模塊化存儲陣列：這些系統連接在一個使用串行 ATA磁盤的存儲網絡。系統可以是基于塊的存儲陣列，也可以是接在網絡上的NAS網關和服務器。

公共虛擬層：存儲被組織成一個邏輯資源庫，以供用戶使用。

數據冗余和可用性：數據的多個拷貝應該存在于網格的節點上，在部件出現故障時保證冗余數據的存取和可用性。

公共管理：對所有節點的單一管理層次應該覆蓋數據安全、機動性和遷移性、按需能力供應和預備功能等諸多方面。

簡化的平臺 /管理架構: 由于公共的管理非常重要，管理中所涉及的任務應該按模塊方式組織好，允許自動發現網格中的節點和自動完成卷及文件的管理。

三大基本優勢

將網格拓撲應用于存儲網絡帶來了諸多的好處，其中包括下列優勢：

可靠性 : 一個設計良好的網格極具彈性。網格不只是在任何兩個節點之間提供兩個通道，而是在每個存儲節點之間提供多個通道。這就使維修服務和出故障時更換部件比較容易，對系統的可用性或宕機時間影響最小。

性能：導致高可靠性的因素同樣也能改善性能。不需要有大量端口的集中式交換機，消除了潛在的性能瓶頸，并能將負載平衡技術應用于可使用的多個通道，為整個網絡提供一致的性能。

可擴展性 : 利用端口數不多的廉價交換機，就能很容易地擴展網格網絡，以適應為提高性能、帶寬和容量而增加的服務器。本質上，網格存儲是利用較廉價的存儲設備來向外擴展而不是向上升級的方法。