Storage for Kata Containers - 9pfs vs virtio-blk

9pfs (virtio-9p) ## virtio-blk ## When to use which 9pfs (Plan 9 File System via virtio-9p) and virtio-blk are two different methods for providing storage to virtual machines, differing primarily in their level of abstraction (file-level vs. block-level). 9pfs exposes a specific directory on the host machine directly to the guest. It is often used for "shared folders" where the host and guest need simultaneous access to the same files. This presents a virtual raw block device (a "hard drive") to the guest. The guest OS treats it like a physical disk and manages its own filesystem (e.g., ext4, XFS) on top of it. Templates let you quickly answer FAQs or store snippets for re-use. Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink. Hide child comments as well For further actions, you may consider blocking this person and/or reporting abuse - Elasticity: Storage is only consumed by actual files on the host; no need to pre-allocate a large image file. - Ease of Use: Useful for development, where you want to edit code on the host and run it immediately in the guest. - Performance: Generally slower than block devices because every file operation must go through the 9P protocol and host system calls. - Compatibility: While Linux support is excellent, Windows support is limited and often requires third-party drivers. - Modern Alternative: virtio-fs is the successor to 9pfs in many modern QEMU setups, offering significantly better performance and POSIX compliance. - High Performance: Optimized for low latency and high throughput. Features like IOThread Virtqueue Mapping (introduced in QEMU 9.0) allow it to scale across multiple vCPUs efficiently. - Full Feature Support: Supports TRIM/Discard (to reclaim space), bootable partitions, and standard disk management tools. - Isolation: The host cannot easily "see" or edit files inside the block device while the guest is running without risking corruption. - Fixed Size: Typically requires pre-allocation or using "sparse" image formats (like QCOW2) which can have their own performance trade-offs. - You need to share a host directory into a guest for development, simple file exchange, or testing. - You value ease of sharing over raw performance and strict isolation.​ - You are provisioning a root disk or data disk for a VM. - You care about performance, isolation, and standard disk semantics (snapshots, independent filesystems per VM).​