Block device caching strategies, default to “Unsafe”.
Firecracker offers the possiblity of choosing the block device caching strategy.
Caching strategy affects the path data written from inside the microVM takes to the host persistent storage.
Block device IO engine, default to “Sync”.
The Async engine leverages io_uring for executing requests in an async manner,
therefore getting overall higher throughput by taking better advantage of the block device hardware, which typically supports queue depths greater than 1.
The block IO engine is configured via the PUT /drives API call (pre-boot only), with the io_engine field taking two possible values: