10 October 2012

DB2 PureScale

          IBM DB2 PureScale High Availability!

In October 2009, IBM announced a new technology, primarily aimed at online transaction processing (OLTP) scale-out clusters, called IBM DB2 pureScale. DB2 pureScale is a new feature that provides scale out active-active services for IBM DB2 running on AIX on Power Systems servers. It's designed to deliver the highest levels of distributed availability and scalability wrapped in a well-thought-out, up-and-running path that's much easier to operate than other clustered database systems.

The DB2 pureScale Feature meets the needs of many customers by providing the following key benefits:

Virtually unlimited capacity
The DB2 pureScale Feature provides practically unlimited capacity by enabling the addition and removal of members on demand. The DB2 pureScale Feature can scale to 128 members. It has a highly efficient, centralized management facility that allows for very efficient scale out capabilities. The DB2 pureScale Feature also leverages a technology called Remote Direct Memory Access (RDMA) that provides a highly efficient inter-node communication mechanism to augment its scaling capabilities

Application transparency
An application that runs in a DB2 pureScale environment does not need to have any knowledge of the different members in the cluster or of partitioning data. The DB2 pureScale Feature automatically routes applications to the members deemed most appropriate. The DB2 pureScale Feature also provides native support for syntax that other database vendors use, which enables those applications to run in a DB2 pureScale environment with minimal or no changes.

Continuous availability
The DB2 pureScale Feature provides a fully active-active configuration such that if one member goes down, processing continues at the remaining active members. During a failure, only data being modified on the failing member is temporarily unavailable until database recovery completes for that set of data, which is very quick. This is an advantage over some competing solutions in which an entire system freeze occurs as part of the database recovery process.

Reduced total cost of ownership
The DB2 pureScale interfaces easily handle the deployment and maintenance of components integrated within the DB2 pureScale Feature. This helps reduce what might amount to steep learning curves associated with deploying and maintaining with some competing technologies.

To understand these benefits, it helps to understand the basic architecture. Clients connect to a single database view comprised of four cluster members with shared storage. The clients connect anywhere. The DB2 member runs on several host computers with integrated cluster services. The members are connected over low-latency, high-speed connections to the PowerHA pureScale server. The logs and data-sharing architecture are centralized for all the clients. The figure below depicts the components that make up the DB2 pureScale configuration. Even though there are several advanced components, a significant portion of this architecture is transparent to the end user, because the DB2 pureScale Feature internally deploys and manages these components.

DB2 pureScale Feature topology overview

In the Figure for Architecture Overview, clients can connect to any member. The DB2 pureScale Feature can automatically load balance the clients across the different members based on the utilization of each computer. If any host in the configuration fails, the DB2 pureScale Feature redirects clients among the active members on the remaining hosts.

Each DB2 member represents a DB2 processing engine. Up to 128 members can be deployed in a single DB2 pureScale configuration. The members cooperate with each other and with the PowerHA pureScale server to provide coherent access to the database from any member. Members can be added and removed as processing demands change. Modifications to the number of active members can be done without any impact to the clients.

Integrated with the DB2 pureScale Feature is a cluster services layer that provides failure detection, recovery automation, and a clustered file system. These technologies are integrated within the DB2 pureScale Feature, and they leverage IBM technologies optimized for DB2 software. The technologies include IBM Tivoli® Systems Automation for Multi-platforms (Tivoli SA MP), Reliable Scalable Cluster Technology (RSCT), and General Parallel File System (GPFS™). The DB2 pureScale Feature automatically deploys and configures these technologies according to a best-practice, pre-defined configuration. A customer does not need to determine how to configure the clustering technology that comes with the DB2 pureScale Feature, because the end user doesn't see it.
In the DB2 pureScale configuration, there is a need for communication between the members and the PowerHA pureScale servers. To make this communication as efficient as possible, the DB2 pureScale Feature leverages the RDMA technology. RDMA allows one computer to read or write to the memory of another computer without requiring any processor cycles on the target machine. This mechanism, in conjunction with extremely high-speed networks such as InfiniBand, allows for an extremely efficient transport layer, which enables the DB2 pureScale Feature to scale efficiently.

The PowerHA pureScale servers (also referred to as CF) provide a scalable and centralized locking mechanism to ensure data coherency. The servers also act as a fast cache for DB2 pages, leveraging RDMA technology to provide increased performance in situations where a physical disk operation might otherwise have been required. The PowerHA pureScale server and the efficient transport layer are two of the features that enable the DB2 pureScale Feature to scale so well, because each member does not have to negotiate with all other members when performing a task.

The DB2 pureScale Feature leverages a shared-disk technology. Any member can read or write to any portion of the database. If any member fails, the full set of data is still accessible from the other active members.

DB2 pureScale

DB2 pureScale: Availability Demo

Using Data Replication for Continuous Availability

Download DB2 10.1:

Drs. Albert Spijkers
DBA Consulting
web:            http://www.dbaconsulting.nl
email:           albertspijkers@dbaconsulting.nl


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