A DR site less than 15 km from the primary data centre is insufficient to guard against area disasters and pandemics, because it is possible that neither the data centre nor the DR site would be accessible. A common guideline calls for 150 km of separation.
Asynchronous site-to-site data replication moves data offsite not to tape but to disk drives, which can significantly reduce recovery time. Most backup/recovery applications can back up to disk using compression and/or de-duplication technology to reduce the size of the backup image. With change-only backup methods, transmission bandwidth and data storage requirements are minimised. Virtual tape libraries (VTLs) are specialised storage devices that can further automate the DR process.
Synchronous data replication ensures that all data entered or changed is simultaneously replicated. This is typically the most expensive off-site replication option, but may be justified for some critical applications. Synchronisation delivers an immediate RPO and an RTO limited to the time that it takes to declare a disaster, restart the application from the second site and re-establish communication.
4. Auditing Cloud Providers
IT organisations should also understand the data protection solutions offered by the provider. Most offer daily backup to disk, with some also offering periodic tape backup. However, these backups are usually on-site; off-site tape transfer is rarely included in the base service. While on-site backups can help recovery from data corruption and inadvertent data deletion, and allow point-in-time restores, they provide little protection from disasters.
IT managers should compare service provider DR documentation options to their own requirements, just as they would for their own data centre. Elements to audit include the location of the data centre, possible events that could compromise it, the availability of power and communications, the data centre's relationship to recovery destinations, data centre hardening features and the vendor's DR contingencies. Make sure your cloud provider has a process for simulating and testing your DR solution and ensuring it performs as promised.
5. Implementing and Managing
IT environments evolve as applications are added, terms of service change and cloud vendors get acquired. So it's important to continually test your cloud disaster recovery solution. A rolling quarterly DR test on a subset of applications may be sufficient, as long as most or all of your systems are also tested annually. Plan a comprehensive annual audit of your cloud DR solution to assure it meets your evolving needs.
IT infrastructure can fail, regardless of whether it is in-house or in the cloud. The onus is on IT managers to have the right disaster recovery solution in place to avoid the serious damage an outage can cause their business. With the right planning, analysis of options and precautionary measures, IT managers can make the cloud much safer for their business operations - and more productive for their organisation.
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