Oracle’s Autonomous Database Provides An Added Edge To Performance And Cost

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Gifford Brickley

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Jul 17, 2024, 2:22:37 AM7/17/24

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Oracle Exadata Database Machine (Exadata) is an engineered system that delivers the ideal platform for running Oracle Database workloads at an optimal cost. Its scale-out architecture integrates the latest processors, intelligent storage servers, cutting-edge caching technologies, and advanced networking features. Customers can harness unique hardware and software optimizations of Exadata by running Oracle Autonomous Database and Oracle Exadata Database Service on dedicated Exadata Cloud Infrastructure on Oracle Cloud Infrastructure (OCI) and in Microsoft Azure data centers through the Oracle Database@Azure offering. Additionally, through Oracle Exadata Cloud@Customer, which uses the same architecture and infrastructure as Oracle Exadata Database Machine, customers can bring the performance and economics of Oracle Exadata Database Service and the fully managed Oracle Autonomous Database into their data centers, thereby assisting in meeting data residency or application architecture requirements. Lastly, both the Zero Data Loss Recovery Appliance and Zero Data Loss Autonomous Recovery Service utilize Exadata hardware and software; they simplify Oracle Database backup processes, accelerate database recovery, and increase protection against cyberattacks.

Oracle Linux differentiates itself from alternative Linux distributions by capitalizing on its deep integration with the solution stack. Let's dive deeper and look at a few aspects highlighting how Oracle Linux is the operating environment for Exadata Database Machine.

Oracles autonomous database provides an added edge to performance and cost

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For example, Exadata takes advantage of Remote Direct Memory Access (RDMA) to facilitate direct memory access from the database servers to the storage servers. The required kernel and system packages for this compelling feature are not merely included in Oracle Linux with UEK for Exadata use; they are carefully integrated, rigorously tested, and delivered to help ensure superior performance and security. Exadata's singular focus on being the ideal platform for Oracle Database, combined with co-engineering with the Oracle Linux team, translates to exceptional performance, improved upgrade time, and hardened system security.

Exadata utilizes an RDMA over Converged Ethernet (RoCE) network fabric to connect each database server to every storage server. This network provides low latency and ample bandwidth for rapid data access and transfer rates. Beyond speed, the RoCE fabric includes capabilities such as zero packet loss messaging, direct data access without CPU involvement, and KVM-based virtualization security.

As database workloads grow, the RoCE network fabric plays a central role in Exadata's scale-out architecture. Customers can add additional databases and/or storage servers online to increase performance and capacity. Should the demand exceed the capacity of a single physical rack, multiple racks can be interconnected without downtime to meet the performance, scalability, and availability needs of any environment.

RDMA is an integral part of the high-performance architecture of Exadata and has been continuously enhanced with each successive generation of Exadata, underpinning Exadata-only technologies such as Exadata RDMA Memory (XRMEM) Data Accelerator and Exafusion Direct-to-Wire Protocol. Moreover, it optimizes the efficiency of complex, mission-critical OLTP and analytics workloads, as well as modern applications using JSON, blockchain, spatial, graph, and vector processing within Oracle Database.

To fully leverage Oracle Linux with the minimized UEK and harness the comprehensive features for which Exadata is renowned, specialized software known as ESS is installed and operated on all database and storage servers within the Database Machine. ESS enables a range of features such as XRMEM Data Accelerator, Exadata Smart Flash Cache (Flash Cache), Smart Scan, Storage Indexes, Hybrid Columnar Compression, Database In-Memory Columnar Cache on Storage Servers, and many more.

The XRMEM Data Accelerator is an automatically managed, shared read-accelerator memory cache tier in front of Flash Cache, which enables orders of magnitude lower latency when accessing remotely stored data. Oracle Database uses RDMA to remotely access the XRMEM Data Accelerator memory, bypassing the network and I/O stack on both the database and storage servers. This eliminates costly CPU interrupts and context switches and reduces latency by more than 10X, from 200 μs to as low as 17 μs. Exadata's end-to-end integration between Oracle Database and Exadata Storage Servers automatically caches the hottest data efficiently between the database buffer cache and Flash Cache in the storage servers, thereby increasing the efficacy of RDMA-enabled Oracle Linux with UEK.

Exadata Storage Servers incorporate PCIe Flash Cards, which function as a caching tier between Exadata RDMA Memory and persistent storage, commonly referred to as Exadata Smart Flash Cache. This caching mechanism is used in conjunction with the XRMEM Data Accelerator to automatically cache frequently accessed data, while less frequently accessed data remains on disk. This approach combines the high I/O rates and fast response times of flash with the large capacity and cost efficiency of disk. Exadata possesses a unique understanding of database workloads and can intelligently avoid caching data that negatively impacts overall performance.

Smart Scan, also known as SQL Offload to Storage and exclusive to Exadata, pushes SQL query processing down to the storage servers. It performs tasks such as filtering, column selection, joins, and aggregation within the storage tier, eliminating the need to bring all queried data to the database tier to begin with. Conventional storage arrays only deliver a fraction of the aggregate bandwidth available from their flash drives due to the network link between the database server and storage becoming a significant bottleneck.

A key database format-aware storage server optimization is the Storage Index. When smart scans run on storage servers, they populate an in-memory metadata cache that records the ranges of column values stored within each of the data units accessed by the scan. This metadata can be used by future smart scans to determine, based on their filter predicates, whether to visit or skip a certain data unit. As a result, there can be a significant reduction in the number of storage I/O operations issued by the smart scan, depending on the selectivity of the filter.

Exafusion is the next-generation networking protocol uniquely available on Oracle Exadata. Oracle Database utilizes Exafusion to eliminate context switching and minimize OS overhead through direct-to-wire messaging, yielding a 3X improvement in latency compared to non-Exadata platforms relying on traditional messaging models. Additionally, there is a substantial reduction in CPU utilization associated with inter-instance communications. Overall, this acceleration in messaging directly benefits application performance, particularly for those deployed on Oracle Real Application Clusters (RAC).

When deployed on Exadata, Oracle Database maintains an In-Memory Commit Cache. Each Oracle RAC instance maintains a cache of local transactions and commit state, which remote instances can read using RDMA. This commit cache facilitates bulk transaction state lookup, which reduces single transaction lookup messages and substantially improves both query and DML processing time.

Exadata database servers leverage the Oracle Ksplice zero-downtime capability of Oracle Linux to apply security patches while the OS stays online, meaning that no workloads or systems need to be interrupted. For the Exadata Database Machine, customers can use Ksplice to apply updates to the kernel on database servers. For Exadata Cloud@Customer, when possible, updates deployed by Oracle are applied to running systems without downtime through the use of Ksplice. For other updates that require a component restart, Oracle performs the component restart in a rolling fashion to help ensure service availability during the update process.

Exadata's Linux configuration exceeds 90% on the Defense Information Systems Agency (DISA) Security Technical Implementation Guide (STIG) Security Content Automation Protocol (SCAP) benchmark right out of the factory. Coupled with Exadata-optimized Linux security features such as Secure Boot, Advanced Intrusion Detection Environment (AIDE), Security Enhanced Linux (SELinux), LDAP, Kerberos support, Federal Information Processing Standard (FIPS) 140-2 support, Secure Computing (seccomp) on Storage Servers, and the full suite of Oracle Database security features, Exadata delivers end-to-end data protection without compromising performance or availability.

Gursewak Sokhi is a Technical Product Manager for Oracle Linux and Virtualization. He holds a Computer Engineering B.S. with a concentration in Systems Programming, and a Mathematics and Economics B.A. from the University of California, Santa Cruz.

Alex Blyth is a Product Manager for Oracle Exadata with over 25 years of IT experience mainly focused on Oracle Database, Engineered Systems, manageability tools such as Enterprise Manager and most recently Cloud. Prior to joining the product management team, Alex was a member of the Australia/New Zealand Oracle Presales community and before that a customer of Oracle's at a Financial Services organisation.