计算机专业时文选读之一

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.

时文选读

网格存储

定义：网格存储与网格计算类似，是部署和管理分布在多个系统和网络上的存储的新模式，在无需集中式大型交换系统的情况下，高效地利用可资使用的存储容量。

网格实际上是一个网状网络，其中没有控制路由的单个集中式交换机或集线器。网格在规模和性能上提供了无限的扩展性，因为它们不会受越来越大的集中式中央交换机这个需求的束缚。因此，网格网络降低了构件的成本，生成一个可靠且有弹性的结构。

将网格概念应用于计算机网络，让我们通过动态分配和重新分配数量众多的分布式计算机的容量、带宽和处理能力，利用可用但未用的资源。计算网格可以跨越地域、机构、机器架构和软件界限，给连接着的用户提供处理能力、协作和信息存取。大学和研究机构正在利用网格提供 PC机、苹果机和Linux机组成的、可与巨型机匹敌的计算能力。

有了网格计算之后，出现利用分布数据存储的类似模型只是个时间问题。大多数存储网络是星型结构，其中所有服务器和存储设备都与单一的中央交换机相连。相反，网格的拓扑结构是互联在一起的小服务器网络，可以随着带宽的增加而增加服务器，继续提供更好的可靠性和更高的性能及连接性。

何为网格存储?

基于目前已有的和建议中的产品，网格存储系统应该包括下列组成部分：

模块化存储阵列：这些系统连接在一个使用串行 ATA磁盘的存储网络。系统可以是基于块的存储阵列，也可以是接在网络上的NAS网关和服务器。

公共虚拟层：存储被组织成一个逻辑资源库，以供用户使用。

数据冗余和可用性：数据的多个拷贝应该存在于网格的节点上，在部件出现故障时保证冗余数据的存取和可用性。

公共管理：对所有节点的单一管理层次应该覆盖数据安全、机动性和迁移性、按需能力供应和预备功能等诸多方面。

简化的平台 /管理架构: 由于公共的管理非常重要，管理中所涉及的任务应该按模块方式组织好，允许自动发现网格中的节点和自动完成卷及文件的管理。

三大基本优势

将网格拓扑应用于存储网络带来了诸多的好处，其中包括下列优势：

可靠性 : 一个设计良好的网格极具弹性。网格不只是在任何两个节点之间提供两个通道，而是在每个存储节点之间提供多个通道。这就使维修服务和出故障时更换部件比较容易，对系统的可用性或宕机时间影响最小。

性能：导致高可靠性的因素同样也能改善性能。不需要有大量端口的集中式交换机，消除了潜在的性能瓶颈，并能将负载平衡技术应用于可使用的多个通道，为整个网络提供一致的性能。

可扩展性 : 利用端口数不多的廉价交换机，就能很容易地扩展网格网络，以适应为提高性能、带宽和容量而增加的服务器。本质上，网格存储是利用较廉价的存储设备来向外扩展而不是向上升级的方法。