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分类: 数据仓库与数据挖掘

2017-10-14 08:41:26


Shared-nothing multiplex is a multiplex storage architecture for massively parallel processing of big data, wherein primary data is stored on a set of direct-attached storage (DAS) devices spread across a set of servers, rather than on a shared storage area network (SAN).

A traditional SAP IQ multiplex accesses base data through shared disks, and transmits intermediate query results through shared temporary disks or across the network. Queries scale well until the shared disk bandwidth is saturated. Shared nothing multiplex leverages local disk bandwidth to scale I/O performance with cluster size.

Like all multiplex features, shared-nothing multiplex requires the multiplex grid license. No additional licenses are required.

Shared-nothing multiplex is a DQP (distributed query processing) technology. A properly-distributing query is a prerequisite for efficient use of direct-attached storage (DAS). Shared-nothing multiplex introduces a new kind of dbspace, called a DAS dbspace. A DAS dbspace is composed of DAS dbfiles, and is associated with a logical server, a subset of physical servers within an IQ multiplex. DAS dbspaces are best suited for storing large IQ tables, such as fact tables in a star schema. Such tables can be partitioned and placed on local storage across the logical server. Query processing on these partitioned tables can be highly distributed for massive parallel processing.

The SAP IQ database can concurrently support both shared-disk storage and shared-nothing, or "DAS," storage. You can mix and match shared and shared-nothing dbspaces according to your needs. Moreover, a shared-nothing multiplex supports shared file system (SFS) primary DAS dbfiles; for example, you can add Network File System (NFS) DAS dbfiles to the DAS dbspace in your logical server.Note that with a shared nothing multplex, you still need shared storage for your IQ_SYSTEM_MAIN dbspace. You can use either NFS or a SAN for this shared dbspace.

Note

  • Shared-nothing multiplex is not supported on Windows platforms in this release of SAP IQ.

  • Shared-nothing multiplex does not support point-in-time recovery in this release of SAP IQ.

  • Shared-nothing multiplex does not support row-level versioning (RLV) in this release of SAP IQ. 


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