DragonFly On-Line Manual Pages

NEWFS_HAMMER(8)        DragonFly System Manager's Manual       NEWFS_HAMMER(8)


newfs_hammer -- construct a new HAMMER file system


newfs_hammer -L label [-Ef] [-b bootsize] [-m savesize] [-u undosize] [-V version] special ...


The newfs_hammer utility creates a HAMMER file system on device(s) special. If multiple devices are specified a single HAMMER file system is created which spans all of them. Each special will constitute a vol- ume which the HAMMER file system is built on. HAMMER file systems are sector-size agnostic, however the DragonFly implementation requires the sector size to be no larger than 16K. HAMMER file systems start at a relative offset of 0 and may only be created under out-of-band disk labels (disklabel64(5) or gpt(8) labels), or in disklabel32(5) partitions which do not overlap the label area (have a starting sector greater than 16). HAMMER file systems are designed for large storage systems, up to 1 Exabyte, and will not operate efficiently on small storage systems. The minimum recommended file system size is 50GB. HAMMER must reserve 500MB to 1GB of its storage for reblocking and UNDO/REDO. In addition, HAMMER file systems operating normally, with full history retention and daily snapshots, do not immediately reclaim space when files are deleted. A regular system maintenance job runs once a day by periodic(8) to handle reclamation. HAMMER works best when the machine's normal workload would not otherwise fill the file system up in the course of 60 days of operation. The options are as follows: -L label All HAMMER file systems must be named and names should be unique on a per-machine basis. -b bootsize Specify a fixed area in which a boot related kernel and data can be stored. The bootsize is specified in bytes. By default a boot area of approximately 4MB will be created. -f Force operation. This is needed for the creation of a HAMMER file system less than 10GB size or with less than 500MB UNDO/REDO FIFO. This should not be used under normal circumstances. -E Use TRIM to erase the device's data before creating the file sys- tem. The underlying device must have the TRIM sysctl enabled. Only devices that support TRIM will have such a sysctl option (kern.cam.da.X.trim_enabled). -m savesize Specify a fixed area which HAMMER may use as a memory log. This area is currently unused. The savesize is specified in bytes. -u undosize Specify the size of the fixed UNDO/REDO FIFO. The undosize is specified in bytes. By default 0.1% of the root volume's size is used, with a reasonable minimum and a reasonable cap. The UNDO/REDO FIFO is used to sequence meta-data out to the media for instant crash recovery. -V version Specify the HAMMER file system version to format. By default newfs_hammer formats the file system using the highest production version number supported by the HAMMER VFS by checking the vfs.hammer.supported_version sysctl. If you need to maintain compatibility with an older version of HAMMER you may specify the version with this option. The bootsize, savesize and undosize must be given with a suffix of K, M, G or T meaning kilobyte, megabyte, gigabyte and terabyte. Lower case can also be used for suffix.


newfs_hammer -L Home /dev/ad0s1d Create a file system named `Home' on /dev/ad0s1d.


Exit status is 0 on success and 1 on error.


disklabel32(5), disklabel64(5), HAMMER(5), fdisk(8), gpt(8), newfs(8)


The newfs_hammer utility first appeared in DragonFly 1.11.


Matthew Dillon <dillon@backplane.com> DragonFly 4.3 October 7, 2011 DragonFly 4.3