SQL Backup/Restore and Disaster Recovery solutions with VMware

Question

Is vSphere Replication safe for SQL databases?

We are a virtual environment (Cisco hardware + VMware hosts + HP san).
We have a primary and disaster recovery datacenter, with SAN-level replication already setup for every 4-hours.

There are several HA/DR solutions for SQL - alwayson, logshipping, clustering, replication etc. But we want the easiest administrative solution that can deliver good RPO & RTO. So we're looking to replicate at the VM-level instead of SQL-level strategies.

Apparently, any VM-level snapshot/backup solution needs to be VSS (Microsoft's volume shadow service) aware to ensure highly transactional applications like Exchange or SQL Server comes back up in a consistent state after restore.

VMWare's SRM(Site Recovery Manager) gives you the choice of array based replication or vSphere Replication. I read here that vSphere Replication is VSS aware and can offer utmost 15 minute RPO, which is very acceptable for most of our applications.

Does anyone else use this for enterprise oltp applications with 15-minute DR RPO (not high-availability) ? Does it freeze IO on SQL server for unusable period of time ? Does it definitely ensure consistency when VM turns back on at the DR site ?

Answer 1

VMware HA is not database server high availability...

Read Brent Ozar's article on the subject.

Answer 2

VMWare SRM works on a block-level basis to ensure file-system consistency. As long as you use the consistency-groups feature to ensure all data and log drives are replicated in perfect order, you can guarantee database-level consistency using this feature.

Ensure you test everything thoroughly before relying on it in case you have something configured incorrectly.

Ensure you reliably create and store SQL Server database backups including log backups, offsite for disaster recovery, even if you cannot meet RTO objectives via this strategy. Having a backup that can be restored, even if it's somewhat late, is far far better than having no backups. In other words, don't rely solely on VMWare SRM replication, or any kind of replication, for disaster recovery.