This post is the second in a Multi-Part Video Series on “Oracle Exadata Cloud Service for DBAs & APPS DBAs“. In this post, I’ll be discussing the Architecture of Exadata Cloud Service (ExaCS).
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Architecture of Exadata Cloud Service
The major components of an Exadata Cloud Service include:
- Database Servers
- Storage Servers
- Oracle Management Console
Note: Depending on the configuration of the Exadata Cloud Service, the number of Database Nodes and Storage Nodes vary. In this post, we’ll be referring to Quarter Rack configuration.
1. Database Servers
Database Servers are the servers where the Oracle Database Instances run. The client has full root access on these Linux Servers. Database Servers can have 2,4 or 8 nodes, depending on the configuration of Exadata Cloud Service. An Exadata Database Server contains at least one Virtual Machine (VM), known as DomU, running on a VM hypervisor or virtual machine monitor(VMM), known as Dom0.
- Dom0. Dom0 is inaccessible by the clients and can only be accessed by the Oracle Team. The resource allocated to Dom0 is minimal. Therefore, it runs on 2 CPUs and 16GB RAM. Oracle uses the Integrated Lights Out Manager (ILOM) which is a highly specialized tool created to manage and monitor servers. ILOM controls the hardware and firmware of the Dom0 Database Server.
- DomU. Users have secure access to DomU. Each DomU is provisioned with a complete Oracle Database installation including all the features of Oracle Database Enterprise Edition, Oracle Grid Infrastructure with Cloud Tools like DBaaSCLI and bkup_api for backup & recovery, etc. In DomU, the client patches and maintains the operating system, grid, Exadata, etc. By default, there are 4 operating system users who can connect OPC user to Exadata Server using the SSH key pair. The four default operating system users are:
Note: Learn How to Create Compute on OCI (The client can use the same method to connect to Exadata using SSH key pair.)
2. Storage Servers
There can be 3,6 or 12 Storage Nodes in an Oracle Exadata Cloud Service Instance. Each Oracle Exadata environment has a storage space inside the Exadata Storage Servers which is used by Oracle Automatic Storage Management (ASM). ASM has multiple disk groups which are:
- Data. The Data disk group is used for storing Oracle Database data files.
- Recovery. The Recovery disk group which is used for storing the Fast Recovery Area (FRA). Here, Oracle Database creates and manages backup and recovery, such as RMAN backups and archived redo log files.
- Sparse. The client can optionally create the Sparse disk group. The Sparse disk group is used for Fast Clone.
Database Servers and Storage Servers are connected to each other by a network of high-bandwidth or high-speed, low-latency, InfiniBands. These InfiniBands are also used for intra-server connections so that the Instances can communicate with each other efficiently.
There are three types of networks in an Oracle Exadata Cloud Service Instance:
- Client Network. This network is used by the Client Applications to securely connect to the Exadata Cloud Servers using either SSH on port 22 or SQLNet on port 1521.
- Backup Network. This network is used to backup or restore Exadata on Oracle’s Object Storage Service. The Client and Backup Networks use bonded network interfaces to maximize performance and availability.
- Management Network. This network is used by the Oracle Team to manage the hardware, firmware, and the Exadata Storage Servers through Oracle Management Console.
5. Oracle Management Console
All hardware, firmware, and the Exadata Storage Servers are managed by the Oracle Team from the back-end using Oracle Management Console and the management network.
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