Oracle Exadata

The Oracle Exadata Database Machine is a combined compute and storage system marketed for running Oracle Database software. Exadata debuted in 2008 as the first in Oracle Corporation's family of "Engineered Systems". Oracle Corporation releases new generations of Exadata roughly once a year.

Exadata combines scale-out compute servers, scale-out storage servers, InfiniBand networking and specialized software, packaged in one or more hardware racks, with various sizing options. Exadata compute servers use Intel Xeon processors or SPARC and the Oracle Linux operating system to run Oracle Database software. Exadata storage servers use Intel Xeon processors to perform block storage functions and also run application software to offload data-intensive database processing into storage closest to the data.

As of October  2015, Exadata was available in the Oracle Cloud as a subscription service, also known simply as the "Exadata Service". Databases deployed in this service include all the features and options of Oracle Database Enterprise Edition. Similarly, all Exadata features and capabilities are included in this service. Oracle databases in the Exadata Service are 100% compatible with databases deployed on-premises, which enables customers to transition to the Cloud with no application changes. Oracle Corporation manages this service – including hardware, network, Linux software and Exadata software –, while customers have complete ownership of their databases.

Use cases

Exadata is designed to run any Oracle Database workload or mix of workloads.

Long running requests, characterized by data warehouse queries or other queries, reports, batch jobs and analytics, are reputed to run many times faster compared to a conventional, non-Exadata database server. Customer references often cite performance gains of 10x or greater. Analytics workloads can also use the Oracle Database In-Memory option on Exadata for additional acceleration. Exadata’s "Hybrid Columnar Compression" feature is intended to reduce the storage consumption of data warehouses and archive data as well as increase performance by reducing the amount of I/O.

Transactional (OLTP) workloads on Exadata benefit from the incorporation of flash memory into Exadata’s storage hierarchy, and the automatic "tiering" of data into memory, flash or disk storage. Special flash algorithms optimize flash for response time sensitive database workloads such as log writes. For high-end OLTP, all-flash storage eliminates the latency of disk media completely.

All Exadata workloads benefit from an internal InfiniBand fabric running a specialized database network protocol called iDB.

Models

Exadata is available in one of two variants: one based on two-socket database servers and the other based on eight-socket database servers. The two models differ only in the hardware used for the compute servers. The networking, storage servers and software are the same in both models.

The most recent Oracle Exadata Database Machine is the X7 generation, introduced in October 2017.

In February 2017 a new SPARC based model, SL6, was released running Linux.

The X7-2 compute servers feature a small form factor, 1 RU (Rack Unit) in height. They employ 2-socket Intel Xeon processors; each socket with 24 compute cores for 48 total cores per compute server. Memory starts at 384 GB and can be expanded to 1.5 TB.

The Exadata Database Machine base configuration has 2 compute servers and 3 storage servers, referred to as a "Quarter Rack". The same hardware is also available in an "Eighth Rack" configuration with half of the processing turned off and half of the storage capacity either turned off or removed until needed. As the database workload and/or data size increases, additional compute and storage servers may be added to increase the volume of work performed in parallel. This is commonly referred to as "scale-out".

The X7-8 compute server uses eight-socket servers that consume 5 RU in height and have greater memory capacity than the X7-2. Whereas each X7-2 compute server contains 48 compute cores, the X7-8 server contains 192 compute cores. This allows large database workloads to easily "scale-up" within a compute server while still supporting Exadata’s "scale-out" expandability across multiple servers. The larger memory capacity of the X7-8 also favors in-memory database and very large OLTP, consolidation, and DW workloads. Like the X7-2, the Exadata X7-8 base configuration has 2 compute servers and 3 storage servers, but consumes a "Half Rack" of space. Additional compute and storage servers may be added until the rack is full.

Storage servers

There are two choices for Exadata storage servers; Extreme Flash and High Capacity. The Extreme Flash is an all-flash storage server containing 8 PCIe flash drives for a total of 51.2 terabytes of raw storage capacity in its current X7-2 configuration. The High Capacity storage server in its current X7-2 configuration contains 12 disks, 10TB each, for a total of 120TB of raw storage capacity. To improve I/O response times, the High-Capacity storage server also employ 25.6TB of PCIe flash to cache active data blocks. Exadata’s Smart Flash Cache, Smart Flash Log, Columnar Flash Cache and Write Back Flash Cache features determine how and when to use flash (see Storage Server Software).

In addition to adding storage servers into an Exadata Database Machine base configuration, storage servers may also be acquired with or added to Exadata Storage Expansion racks.

Storage performance specifications for a full rack Exadata configuration are as follows:

Exadata Storage Server	Scan Rate	Read IOPS	Write IOPS
X6-2 Extreme Flash	300 GB/sec	5,625,000	5,180,000
X6-2 High Capacity	214 GB/sec	4,750,000	4,100,000

Note: Based on an elastic configuration of 12 storage servers, 10 compute servers. IOPS = 8K I/O Operations per Second from SQL

Networking

The Exadata Database Machine provides high-speed networks for internal and external connectivity. A 40 Gb/Sec InfiniBand network is used for internal connectivity between compute and storage servers and 10Gb/Sec and 1Gb/Sec Ethernet ports are included for data center connectivity. The InfiniBand network is also used as the cluster interconnect between compute servers. Exadata has a "direct-to-wire" protocol that allows the database to talk directly to the InfiniBand hardware, minimizing operating system overhead.

Options

Prior to the X5-2 generation, Exadata systems were only available in fixed-size configurations of Eighth, Quarter, Half and Full Rack sizes. With the X5-2 Exadata release in January, 2015, "elastic configurations" were introduced. An elastic configuration has a customer-specified combination of database servers and storage servers. Elastic configurations allow individual storage or compute servers to be added to a base configuration until the physical rack is full. For example, an Exadata system optimized for in-memory database processing could be created by adding many compute servers, each with maximum memory. Conversely, an Exadata system optimized for a large data warehouse could be configured by adding many High-Capacity storage servers. The ratio of compute to storage servers can vary, depending on the characteristics of the intended workload. Elastic configurations may also be used to scale out earlier generation Exadata systems using X6-2 servers. In addition, Exadata Database Machines have always been able to span multiple racks using the built-in InfiniBand network connections. Thus, Exadata’s scale-out extends beyond a single physical rack.

Storage server software

Much of the technical differentiation in Exadata is contained in the software that runs in the Exadata storage servers. Unlike conventional storage arrays, Exadata storage servers employ Intel Xeon processors to execute database operations such as scans, joins and filtering; a feature known as Smart Scans. Running query filters directly in storage servers as data streams from disk and flash bypasses network limitations and offloads processing that would otherwise be performed in the database servers.

Storage server software also implements Smart Flash Cache, Columnar Flash Cache, Flash Logging and Write Back Flash Cache routines that use flash storage to improve I/O response times. I/O Resource Management allocates I/O bandwidth to databases or workloads according to specified priorities. Lastly, decompression of Hybrid Columnar Compressed data may be performed in Exadata storage servers.

Compute server software

Exadata compute servers run the Oracle Linux 6 operating system and Oracle Database 11g Release 2 Enterprise Edition or Oracle Database 12c Enterprise Edition. Exadata system resources can be optionally virtualized using the Xen-based Oracle VM. All Oracle Database options, such as Real Application Clusters, Multitenant, Database In-Memory, Advanced Compression, Advanced Security, Partitioning, Active Data Guard and others are optionally available with Exadata. Applications that are certified to a supported version of Oracle Database are automatically compatible with Exadata. No additional modifications or certifications are required.

Management software

Oracle Enterprise Manager 12c (EM) manages Oracle software and hardware, including the Exadata Database Machine. EM integrates with the built-in Exadata management tooling, as well as with customer’s existing systems management and helpdesk tools. Exadata plug-in for EM provides an integrated view of compute servers, storage servers, switches, and topology. In addition, it also provides discovery, monitoring and alerting capability for Exadata systems management.

History

There have been several generations of Exadata products.

Software advances

for analytics Automatically Parallelize and Offload Data Scans to storage Filter Rows in Storage based on 'where' clause Filter Rows in Storage based on columns selected JSON and XML Offload Filter rows in Storage based on Join with other Table Hybrid Columnar Compression Storage Index data skipping I/O Resource Management by User, Query, Service, DB, etc. Automatic Transformation to Columnar Format in Flash Cache Smart Flash Caching for Table Scans Offload Index Fast Full Scans Offloads Scans on Encrypted Data, with FIPS compliance Storage offload for LOBs and CLOBs Storage offload for min/max operations Data Mining Offload All Ports Active InfiniBand Messaging Reverse Offload to DB servers if Storage CPUs are Busy Automatic Data Compression in Flash Cache

for availability Instant Detection of Node or Cell Failure In-Memory Fault Tolerance Sub-second Failover of IO on stuck disk or flash Offload backups to storage servers Exadata Data Validation (H.A.R.D.) Instant data file creation Prioritize rebalance of critical files Automatic Hard Disk scrub and repair Power cycle failed drives to Eliminate false drive failures Avoid reading Predictive failed disks Cell software transparent restart Flash and disk life cycle management alert Confinement of temporarily poor performing drives Prevent shutdown if mirror server is down

for OLTP Database Aware PCI Flash Exadata Smart Flash Logging Write-back Flash Cache I/O Prioritization by DB, User, or workload to ensure QOS Direct-to-Wire Protocol Network Resource Management Exachk full-stack validation Full-stack security scanning NVMe flash interface for lowest latency IO Active AWR includes storage stats for end to end monitoring Database scoped security Cell-to-Cell rebalance preserving flash cache Secure disk and flash erase

Platform

The hardware components are not unique to Exadata. It is the integration of hardware and software components that distinguish Exadata from other database systems.

Exadata generation (2-socket)	v1	v2	X2-2	X3-2	X4-2	X5-2	X6-2	X7-2
Date introduced	Sep-2008	Sep-2009	Sep-2010	Sep-2012	Nov-2013	Jan-2015	Apr-2016	Oct-2017
Operating system	Linux	Linux	Linux	Linux	Linux	Linux	Linux	Linux
Disk storage (raw TB)	168	336	504	504	672	1344	1344	1680
Flash cache (raw TB)	—	5.3	5.3	22.4	44.8	89.6	179.2	358.4
Extreme flash (raw TB)	—	—	—	—	—	179.2	358.4	716.8
Compute cores	64	64	96	128	192	288	352	384
Max memory (Gio)	256	576	1,152	2,048	4,096	6,144	6,144
Ethernet (Gb/sec)	8	24	184	400	400	400	400
Exadata generation (8-socket)	—	—	X2-8	X3-8	X4-8	X5-8	X6-8	X7-8
Date introduced	—	—	Sep-2010	Sep-2012	Jul-2014	Nov-2015	Apr-2016	Oct-2017
Operating system	—	—	Linux	Linux	Linux	Linux	Linux	Linux
Disk storage (raw TB)	—	—	504	504	672	1344	1344	1680
Flash cache (raw TB)	—	—	5.3	22.4	89.6	89.6	179.2	358.4
Extreme flash (raw TB)	—	—	—	—	179.2	179.2	358.4	716.8
Compute cores	—	—	96	160	240	288	288	384
Max memory (TB)	—	—	4	4	12	12	12	12
Ethernet (Gb/sec)	—	—	174	174	184	184	184

External links

• Oracle Steps With Moore’s Law To Rev Exadata Database Machines
• Oracle Exadata Database Machine
• Exadata X5-2 Data Sheet
• Benefits of running E-Business Suite on Exadata and Exalogic
• "History of Exadata", Flash DBA.
• Tanel Poder’s Exadata blog, from an expert in performance tuning on Exadata
• Arup Nanda’s blog, where you can search for Exadata-related posts
• The Enkitec blog, from a company specializing in Exadata and sponsoring yearly Exadata-centric conferences