Zoned block device (ZBD) support has been introduced in Linux with kernel version 4.10. ZBDs have different write constraints than regular block devices. A ZBD is divided into several zones and each zone must be written sequentially.
The main type of ZBD currently available is SMR HDDs. The NVMe Zoned NameSpace proposal is also being drafted to add a zone abstraction to the NVMe specifications.
Natively supporting ZBDs in a filesystem is not a trivial change. Some filesystems must rely on special block layer drivers to ensure sequential writes (e.g. ext4 and the dm-zoned device mappers). Filesystems using a copy-on-write design are better candidates for native ZBD support. Examples are F2FS and btrfs.
This talk discusses the principles of ZBD native support in filesystems. Support in F2FS is discussed and the approach taken with btrfs is next presented. This is followed with a performance comparison between filesystems with native ZBD support and regular ones using dm-zoned.
Naohiro Aota is working at the System Software Group within Western Digital Research. He is working on zoned block device support for file systems like btrfs. He presented the on-going btrfs work at LSFMM 2019.
Damien Le Moal manages the System Software Group within Western Digital Research. Damien is a regular contributor to Linux kernel block I/O stack and file system support for the ZBC and ZAC standards (zoned block devices) and is a maintainer of the kernel dm-zoned device mapper and... Read More →
