By JoeMeeks on Jul 16, 2014
In the first installment of this series we discussed how one size does not fit all when it comes to HA architecture. We described Oracle Maximum Availability Architecture (Oracle MAA) best practices that define four standard reference architectures for data protection and high availability: BRONZE, SILVER, GOLD and PLATINUM. Each reference architecture uses an optimal set of Oracle HA capabilities that reliably achieve a given service level (SLA) at the lowest cost. As you progress from one level to the next, each architecture expands upon the one that preceded it in order to handle an expanded fault domain and deliver a high level of service.
This article provides details for the Bronze reference architecture.
Bronze is appropriate for databases where simple restart or restore from
backup is ‘HA enough’. It uses single instance Oracle database (no
cluster) to provide a very basic level of HA and data protection in
exchange for reduced cost and implementation complexity. An overview is provided in the figure below.
When a database instance or the server on which it is running fails, the recovery time objective (RTO) is a function of how quickly the database can be restarted and resume service. If a database is unrecoverable the RTO becomes a function of how quickly a backup can be restored. In a worst case scenario of a complete site outage additional time is required to provision new systems and perform these tasks at a secondary location, in some cases this can take days.
The potential data loss if there is an unrecoverable outage (recovery point objective or RPO), is equal to the data generated since the last backup was taken. Copies of database backups are retained locally and at a remote location or on the Cloud for the dual purpose of archival and DR should a disaster strike the primary data center.
Major components of the Bronze reference architecture and the service levels achieved include:
Oracle Database HA and Data Protection
- Oracle Restart automatically restarts the database, the listener, and other Oracle components after a hardware or software failure or whenever a database host computer restarts.
- Oracle corruption protection checks for physical corruption and logical intra-block corruptions. In-memory corruptions are detected and prevented from being written to disk and in many cases can be repaired automatically. For more details see Preventing, Detecting, and Repairing Block Corruption.
- Automatic Storage Management (ASM) is an Oracle-integrated file system and volume manager that includes local mirroring to protect against disk failure.
- Oracle Flashback Technologies provide fast error correction at a level of granularity that is appropriate to repair an individual transaction, a table, or the full database.
- Oracle Recovery Manager (RMAN) enables low-cost, reliable backup and recovery optimized for the Oracle Database.
- Online maintenance includes online redefinition and reorganization for database maintenance, online file movement, and online patching.
- Databases deployed using Bronze often include development and test databases and databases supporting smaller work group and departmental applications that are often the first candidates for database consolidation.
- Oracle Multitenant is the MAA best practice for database consolidation from Oracle Database 12c onward.
- Oracle Enterprise Manager Cloud Control enables self service deployment of IT resources for business users along with resource pooling models that cater to various multitenant architectures. It supports Database as a Service (DBaaS), a paradigm in which end users (Database Administrators, Application Developers, Quality Assurance Engineers, Project Leads, and so on) can request database services, consume it for the lifetime of the project, and then have them automatically de-provisioned and returned to the resource pool.
Oracle Engineered Systems
- Oracle Engineered Systems are an efficient deployment option for database consolidation and DBaaS. Oracle Engineered Systems reduce lifecycle cost by standardizing on a pre-integrated and optimized platform for Oracle Database that is completely supported by Oracle.
Bronze Summary: Data Protection, RTO, and RPO
Table 1 summarizes the data protection capabilities and service levels provided by the Bronze tier. The first column indicates when validations for physical and logical corruption are performed:
- Manual checks are initiated by the administrator or at regular intervals by a scheduled job.
- Runtime checks are automatically executed on a continuous basis by background processes while the database is open.
- Background checks are run on a regularly scheduled interval, but only during periods when resources would otherwise be idle.
- Each check is unique to Oracle Database using specific knowledge of Oracle data block and redo structures.
Table 1: Bronze - Data Protection
|Type||Capability||Physical Block Corruption
||Logical Block Corruption
|Manual||Dbverify, Analyze||Physical block checks||Logical checks for intra-block and inter-object consistency|
|Manual||RMAN||Physical block checks during backup and restore||Intra-block logical checks|
|Runtime||Database||In-memory block and redo checksum||In-memory intra block logical checks|
|Runtime||ASM||Automatic corruption detection and repair using local extent pairs||
|Runtime||Exadata||HARD checks on write||HARD checks on write|
|Background||Exadata||Automatic HARD Disk Scrub and Repair||
Note that HARD validation and the Automatic Hard Disk Scrub and Repair (the last two rows of Table 1) are unique to Exadata storage. HARD validation ensures that Oracle Database does not write physically corrupt blocks to disk. Automatic Hard Disk Scrub and Repair inspects and repairs hard disks with damaged or worn out disk sectors (cluster of storage) or other physical or logical defects periodically when there are idle resources.
Table 2 summarizes RTO and RPO for the Bronze tier for various unplanned and planned outages.
Table 2: Bronze - Recovery Time and Data Loss Potential
|Type||Event||Downtime||Data Loss Potential
|Unplanned|| Database instance failure
|Unplanned|| Recoverable server failure
||Minutes to an hour
|Unplanned||Data corruptions, unrecoverable server failure, database failures, or site failures
||Hours to days
||Since last backup
|Planned||Online file move, online reorganization and redefinition, online patching
|Planned||Hardware or operating system maintenance and database patches that cannot be performed online
||Minutes to hours
|Planned||Database upgrades: patch sets and full database releases
||Minutes to hours
||Hours to a day
|Planned||Application upgrades that modify back-end database objects
||Hours to days
So when would you use bronze? Bronze is useful when users can wait for a backup to be restored if there is an unrecoverable outage and accept that any data generated since the last backup was taken will be lost. The Oracle Database has a number of included capabilities described above that provide unique levels of data protection and availability for a low-cost environment based upon the Bronze reference architecture.
But what if I can't accept this level of downtime or data loss potential - well that is where the Silver, Gold and Platinum reference architectures come in. Bronze is only a starting point that establishes the foundation for subsequent HA reference architectures that provide higher quality of service. Stay tuned for future blog posts that will dive into the details of each reference architecture.