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Oracle Exadata Database Machine

Oracle Exadata Architecture

Exadata Introduction

Oracle Exadata Database Machine X9M-2

The Oracle Exadata Database Machine is engineered to deliver dramatically better performance, cost-effectiveness, and availability for Oracle databases. Exadata features a modern cloud-enabled architecture with scale-out high-performance database servers, scale-out intelligent storage servers with state-of-the-art PCIe flash, leading-edge storage cache using persistent memory, and cloud-scale RDMA over Converged Ethernet (RoCE) internal fabric that connects all servers and storage. Unique algorithms and protocols in Exadata implement database intelligence in storage, compute, and networking to deliver higher performance and capacity at lower costs than other platforms, for all types of modern database workloads, including Online Transaction Processing (OLTP), Data Warehousing (DW), In-Memory Analytics, Internet of Things (IoT), financial, gaming and compliance data management, as well as efficient consolidation of mixed workloads.

Simple and fast to implement, the Exadata Database Machine X9M-2 powers and protects your most important databases. Exadata can be purchased and deployed on-premises as the ideal foundation for a private database cloud, or using a subscription model and deployed in the Oracle Public Cloud or Cloud at Customer with all infrastructure management performed by Oracle. The Oracle Autonomous Database is available on either the Oracle Public Cloud or Cloud at Customer.

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Hardware Architecture

Oracle Exadata Database Machine employs a modern scale-out architecture encompassing database compute, storage, network, and software. Uniquely designed to be the ideal platform to run Oracle Database, Oracle Exadata enables enterprises to add capacity and increase performance as workloads scale.

Oracle Exadata utilizes state-of-the-art hardware and purpose-built software to drive the highest database performance.

Each Database server is directly connected to every other Database and Storage Server in a Clos topology, ensuring the minimum number of hops between components.

Remote Direct Memory Access (RDMA) is an integral architectural component of Exadata. It is enhanced in every generation of hardware, Oracle Database, and Exadata System Software release. RDMA enables one server to interact with memory structures on another server without interacting with the OS and network stack on either machine. Each Database and Storage Server is equipped with RDMA capable network cards that directly read from and write to remote memory with no extra copying or buffering. RDMA is also used by Oracle Database when running on Exadata to optimize communication between Real Application Clusters instances.

Fundamental to the architecture of Exadata is modular, shared, smart storage. Each Storage Server is capable of interpreting and processing data independently. The CPUs in the storage servers do not replace database CPUs. Instead, they accelerate database-intensive workloads similar to how graphics cards accelerate image-intensive workloads. Exadata System Software releases Exadata Storage Server's unparalleled performance without any of the bottlenecks of traditional storage. Automatic caching of data from disk into Exadata Smart Flash Cache & Persistent Memory Data Accelerators (a multi-level tiering of data into high-speed, low-latency storage media) enables staggering performance. Each storage server is accessible from every database server. As a result, Flash and Persistent Memory can be shared effectively across multiple database workloads. By automatically caching data from disk into Flash and Persistent Memory, the benefits of these technologies are available and realized by all workloads.

Co-operative Smart Software

Oracle Exadata is comprised of Database Servers, Storage Servers, high-speed, low-latency network fabric, Oracle Database Software, and Exadata System Software. Together, these five components address the need for Oracle Databases shared-everything architecture of Real Application Clusters (RAC).

Oracle Database, running on the Exadata Database Servers, leverages a purpose-built protocol - iDB - and Remote Direct Memory Access (RDMA) over Converged Ethernet (RoCE) to communicate with the Exadata Storage.

iDB is used to direct Smart IO operations on the Storage Servers. Smart IO includes Smart Scan (SQL Offload), Fast File Initialization, and RMAN Incremental Backup Offload. Exadata essentially can "function ship" or push processing from the database servers to the storage servers rather than move potentially hundreds to thousands of terabytes from disk to database server. When the storage server receives a request to perform a Smart IO, Exadata System Software unpacks the iDB message and executes and processes IO requests locally, including executing portions of Oracle Database code on the storage servers, before sending only the data that satisfies the request back to the database servers for final processing (such as aggregation).

Where iDB is used to offload IO intensive processing, such as backups and Analytic queries, to the storage servers, Exadata also leverages the high-speed RDMA over Converged Ethernet network fabric for OLTP workloads. High Capacity Exadata Storage Servers are equipped with Persistent Memory, NVMe Flash Drives, and traditional hard drives. The Exadata System Software automatically caches data into flash and persistent memory based on incoming workload. This automatically managed caching strategy ensures that the most appropriate device is used to service any IO request.

For example, Incremental Fast Backups are offloaded to the Exadata Storage Server. Because Exadata knows that blocks read during a backup are likely of little use for satisfying IO beyond the backup itself, this data IS NOT cached into either flash or persistent memory. At the same time, the Storage Server will cache blocks in both flash and persistent memory to satisfy read and write database requests for OLTP workloads.

Automatically caching data in this manner enables OLTP and Analytic workloads to run faster and resources to be used more efficiently for individual databases. It also enables high degrees of database consolidation.

Oracle Database and Exadata are engineered together. As such, Oracle Database leverages the hardware and software Exadata provides. OLTP database workloads are a good example of such co-engineering. As mentioned above, Exadata Storage Servers include Persistent Memory and are accessible over the RDMA over Converged Ethernet (RoCE) Network Fabric. As OLTP workloads typically access and modify very small amounts of data - 1 or very few rows - caching this data on a fast device, such as persistent memory ensures the quickest read and write speeds for such data. As Exadata employs scale-out hardware and network architecture, placing this persistent memory in the storage servers ensures all database instances benefit from this cutting-edge technology.

Exadata Database Server

Oracle Exadata System Software runs on all database and storage servers to enable Oracle Database to leverage every aspect of Exadata's hardware and network capabilities.

On each Database Server, in addition to the Oracle Linux Operating System, Oracle Grid Infrastructure (including Automatic Storage Management - ASM), and Oracle Database software and instances, you will find the following processes and library:

  • MS - Exadata System Software Management Server - the primary interface for managing the Exadata Database Server, including hardware and software monitoring, metric collection, alerting, and a command-line interface (DMBCLI).
  • RS - Exadata System Software Restart Server - monitors and restarts the MS process if needed.
  • diskmon.bin - the parent diskmon process that monitors and propagates state information to the DSKM process in each Oracle Database and ASM instance. Performs I/O fencing to protect data integrity.
  • DSKM - diskmon child process. Background process in each database (and ASM) instance.
  • libcell - this is an Exadata-specific library linked into the Oracle Database and Grid Infrastructure that allows Oracle to communicate with the Exadata Storage Servers using iDB commands and RDMA.

Exadata Storage Server

Oracle Exadata System Software runs on all database and storage servers to enable Oracle Database to leverage every aspect of Exadata's hardware and network capabilities.

On each Extreme Flash and High Capacity Storage Server*, in addition to the Oracle Linux Operating System, you will find the following processes and library:

  • MS - Exadata System Software Management Server - the primary interface for managing the Exadata Storage Server, including hardware and software monitoring, metric collection, alerting, and a command-line interface (CELLCLI).
  • RS - Exadata System Software Restart Server- monitors and restarts the MS process if needed.
  • CELLSRV - Exadata Cell Server - The core Exadata System Software component responsibile for the majority of the services provided by the Storage Servers, including (but not limited to) SQL Offload, IO Resource Management, Persistent Memory and Flash Cache tiering, Storage Index creation and maintenance.
  • IORM - IO Resource Manager - A sub-process of the CELLSRV process. Responsible for ensuring multiple databases (non-CDB and Pluggable) can share the same shared IO resources ensuring databases on the same infrastructure do not monopolize IO bandwith and degrade perfomance of other databases.
  • CELLOFLSRVn - Cell Offload Server - A sub-process of the Cell Server processes that provides version-specific Storage Offload functions. Each version of Oracle Database uses an associated version-specific CELLOFLSRV process.

* Exadata System Software is also present on Extended Storage Servers, but SQL Offload and other features are not available without Exadata System Software Licenses.