Downtime-Free Live Migration in a Multitenant Database
- Cite this paper as:
- Michael N., Shen Y. (2015) Downtime-Free Live Migration in a Multitenant Database. In: Nambiar R., Poess M. (eds) Performance Characterization and Benchmarking. Traditional to Big Data. TPCTC 2014. Lecture Notes in Computer Science, vol 8904. Springer, Cham
Multitenant databases provide database services to a large number of users, called tenants. In such environments, an efficient management of resources is essential for providers of these services in order to minimize their capital as well as operational costs. This is typically achieved by dynamic sharing of resources between tenants depending on their current demand, which allows providers to oversubscribe their infrastructure and increase the density (the number of supported tenants) of their database deployment. In order to react quickly to variability in demand and provide consistent quality of service to all tenants, a multitenant database must be very elastic and able to reallocate resources between tenants at a low cost and with minimal disruption. While some existing database and virtualization technologies accomplish this fairly well for resources within a server, the cost of migrating a tenant to a different server often remains high. We present an efficient technique for live migration of database tenants in a shared-disk architecture which imposes no downtime on the migrated tenant and reduces the amount of data to be copied to a minimum. We achieve this by gradually migrating database connections from the source to the target node of a database cluster using a self-adapting algorithm that minimizes performance impact for the migrated tenant. As part of the migration, only frequently accessed cache content is transferred from the source to the target server, while database integrity is guaranteed at all times. We thoroughly analyze the performance characteristics of this technique through experimental evaluation using various database workloads and parameters, and demonstrate that even databases with a size of 100 GB executing 2500 transactions per second can be migrated at a minimal cost with no downtime or failed transactions.