Oracle Exadata Database Machine

Oracle Exadata Architecture

Exadata Introduction

Oracle Exadata Database Machine X10M

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 NVMe flash, leading-edge storage cache using Exadata Remote Direct Memory Access (RDMA) memory (XRMEM), 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 X10M 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 Cloud Infrastructure (OCI) or Cloud@Customer with all infrastructure management performed by Oracle. The Oracle Autonomous Database is available on either the OCI or Cloud@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. All database and storage servers are interconnected with each other, communicating over an intelligent, high-speed, low-latency network fabric.

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 (RAC) 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 enables 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 and Exadata RDMA Memory (XRMEM) (a multi-level tiering of data into high-speed, low-latency storage media) enables staggering performance. Every storage server is accessible from every database server. As a result, flash and XRMEM can be shared effectively across multiple database workloads. By automatically caching data from disk into flash and XRMEM, the benefits of these technologies are available and realized by all workloads.

Cooperative 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 I/O operations on the Storage Servers. Smart I/O 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 I/O, Exadata System Software unpacks the iDB message and executes and processes I/O 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 I/O intensive processing, such as backups and Analytic queries, to the storage servers, Exadata also leverages the high-speed RoCE network fabric for OLTP workloads. High Capacity Exadata Storage Servers are equipped with Exadata RDMA Memory (XRMEM), NVMe Flash Drives, and traditional hard drives. The Exadata System Software automatically caches data into flash and XRMEM based on incoming workload. This automatically managed caching strategy ensures that the most appropriate storage tier is used to service I/O requests.

For example, Incremental Fast Backups are offloaded to the Exadata Storage Server. Since Exadata knows that blocks read during a backup are likely of little use for satisfying I/O beyond the backup itself, this data is not cached into either flash or XRMEM. At the same time, the Storage Server will cache blocks in both flash and XRMEM 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. Oracle Database leverages the hardware and software Exadata provides. Exadata Storage Servers include XRMEM and are accessible over the RoCE network fabric. As OLTP workloads typically access and modify very small amounts of data - one or very few rows - caching this data on a fast device, such as XRMEM ensures the quickest read and write speeds for such data. As Exadata employs scale-out hardware and network architecture, placing the XRMEM 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 (DBMCLI).
  • 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 - 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 SQL Offload, I/O Resource Management (IORM), Exadata RDMA Memory (XRMEM) and Flash Cache tiering, and Storage Index creation and maintenance.
  • IORM - I/O Resource Manager - A sub-process of the CELLSRV process. Responsible for ensuring multiple databases can share the same shared I/O resources, ensuring databases on the same infrastructure do not monopolize I/O bandwidth 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.