Putting all your eggs in one cloud basket is risky, because clouds are not immune to denials of se
ScaleArc: If cloud services are the "white knight" sent to solve IT problems, then database as a service is going to fall short.
Interest in database as a service -- such as Amazon's MySQL re-architected for the cloud, Aurora database service -- is increasing, and Microsoft has jumped into the act with its own relational service, known as Azure SQL.
But cloud operations in themselves will impose new problems on database response times and scalability.
When it comes to being "the white knight of enterprise IT needs… cloud services don't free IT from all concerns about availability and performance, despite marketing to the contrary," wrote the database experts at ScaleArc, a supplier of database load balancing software.
The P in PaaS "does not stand for panacea… In fact, the cloud introduces shortcomings and inefficiencies that can undermine performance and jeopardize uptime," when it comes to database applications, the authors said.
"Millions of users have experienced application lag, data loss, and outages arising from database service limitations baked into platform infrastructures," warns the white paper, A Hazy Horizon: Why the Cloud Doesn’t Solve All Your Uptime and Performance Challenges.
In effect, ScaleArc argues that you need load balancing middleware between you and the cloud database service for it to perform as expected. In the process of doing so, it highlights the chief obstacles to achieving performance and availability with cloud database services. They include: network latency, I/O limitations, scalability, and hypervisor challenges, as well as availability issues.
Want to learn more about Amazon's Aurora and other database services? See AWS Expands Database Migration Services, Expands Replication.
In that order, here's what ScaleArc's experts had to say about each:
Network latency: A cloud database server to some extent is only as good as its proximity. How far away is the cloud data center with the database server? The server and its storage could be across town on a high-speed fiber optic loop or they could be hundreds of miles away. "Enterprises have no control over the number of or distance between their network hops," the authors warned.
Cloud services with a data center in a region near you are more likely to offer the lowest latencies due to network delays imposed by distance. By 2025, there will be 485 cloud centers in the world, according to Cisco's Global Cloud Index, so chances are one is coming to a location near you, if there isn't one available already.
In the meantime, network hop latencies impose delays that can cause a database system in the process of updating synchronized data to malfunction. If network latency passes a tolerable threshold, "multiple reconnect attempts may ensue. For some applications, this step might require re-authenticating to the server with each connection attempt." When that happens, kiss effective user response time goodbye.
If the database system is synchronizing with a copy in a different geographical region, that synchronization may be speedy or slow, depending on the subsystem's operation and network connection. If the lag exceeds the customer's "threshold for freshness of data," the primary system needs some way of deciding whether there is another replication point available in a better timeframe, the authors said.
I/O limitations: Not everyone realizes when they sign up for a cloud database service that there will be limitations on their number of I/Os. "The more highly shared the resources, the worse the issues become," said the ScaleArc experts, especially if the service provider makes no effort to police noisy neighbors that create a lot of I/O traffic. If the cloud provider is trying to spread use of existing resources across more customers, yielding more profit, it will contribute to the problem.
