Hello everyone,
Performance optimization is a common objective when designing cloud infrastructure. In Azure, one of the techniques available for improving VM startup speed and disk performance is the use of Ephemeral OS Disks.
A recent enhancement introduces the ability to use full caching with Ephemeral OS Disks for Virtual Machines and VM Scale Sets, offering improved performance characteristics for specific workload scenarios.
What ephemeral OS disks provide
Unlike traditional managed disks, ephemeral OS disks are stored directly on the VM’s local storage instead of remote Azure storage. This design reduces latency and can significantly improve disk performance.
Because the disk resides on the local host, it also enables faster VM provisioning and re-imaging operations.
Full caching capability
The new capability enables full caching behavior for ephemeral OS disks, allowing the operating system disk to benefit from local caching mechanisms.
This approach can improve I/O performance and reduce the dependency on remote storage layers, which can be beneficial for workloads that require rapid scaling or frequent instance recreation.
Typical scenarios
Ephemeral OS disks are particularly useful in environments where VMs are stateless or can be recreated automatically.
Examples include scale-out compute environments, container hosts, batch processing nodes, and other workloads where the operating system disk does not contain critical persistent data.
Final thoughts
The addition of full caching support further enhances the flexibility of ephemeral OS disks in Azure.
For architects designing high-performance or highly scalable compute platforms, this feature provides another option for optimizing VM provisioning speed and disk performance.