TRIM support

[dragonfly.git] / sbin / newfs_hammer / newfs_hammer.8

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.\" by Matthew Dillon <dillon@backplane.com>
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.\" $DragonFly: src/sbin/newfs_hammer/newfs_hammer.8,v 1.10 2008/07/27 16:47:19 thomas Exp $
.Dd April 10, 2011
.Dt NEWFS_HAMMER 8
.Os
.Sh NAME
.Nm newfs_hammer
.Nd construct a new HAMMER file system
.Sh SYNOPSIS
.Nm
.Fl L Ar label
.Op Fl fE
.Op Fl b Ar bootsize
.Op Fl m Ar savesize
.Op Fl u Ar undosize
.Op Fl V Ar version
.Ar special ...
.Sh DESCRIPTION
The
.Nm
utility creates a
.Nm HAMMER
file system on device(s)
.Ar special .
If multiple devices are specified a single
.Nm HAMMER
file system is created
which spans all of them.
Each
.Ar special
will constitute a volume which the
.Nm HAMMER
file system is built on.
.Nm HAMMER
file systems are sector-size agnostic, however the
.Dx
implementation requires the sector size to be no larger than 16K.
.Nm HAMMER
file systems start at a relative offset of 0 and may only be created
under out-of-band disk labels
.Po
.Xr disklabel64 5
or
.Xr gpt 8
labels
.Pc ,
or in
.Xr disklabel32 5
partitions which do not overlap the label area (have a starting sector
greater than 16).
.Pp
.Nm 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.
.Nm HAMMER
must reserve 500MB to 1GB of its storage for reblocking and UNDO/REDO.
In addition,
.Nm 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
.Xr periodic 8
to handle reclamation.
.Pp
.Nm 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.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl L Ar label
All
.Nm HAMMER
file systems must be named and names should be unique on a
per-machine basis.
.It Fl b Ar bootsize
Specify a fixed area in which a boot related kernel and data can be stored.
The
.Ar bootsize
is specified in bytes.
By default a boot area of approximately 4MB will be created.
.It Fl f
Force operation.
This is needed for the creation of a
.Nm HAMMER
file system less than 10GB size or
with less than 500MB UNDO/REDO FIFO.
This should not be used under normal circumstances.
.It Fl E
Use TRIM to erase the device's data before creating the file system. 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).
.It Fl m Ar savesize
Specify a fixed area which
.Nm HAMMER
may use as a memory log.
This area is currently unused.
The
.Ar savesize
is specified in bytes.
.It Fl u Ar undosize
Specify the size of the fixed UNDO/REDO FIFO.
The
.Ar 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.
.It Fl V Ar version
Specify the
.Nm HAMMER
file system version to format.
By default
.Nm
formats the file system using the highest production version number
supported by the
.Nm HAMMER
VFS by checking the
.Va vfs.hammer.supported_version
sysctl.
If you need to maintain compatibility with an older version of
.Nm HAMMER
you may specify the version with this option.
.El
.Pp
The
.Ar bootsize ,
.Ar savesize
and
.Ar undosize
must be given with a suffix of
.Cm K , M , G
or
.Cm T
meaning kilobyte, megabyte, gigabyte and terabyte.
Lower case can also be used for suffix.
.Sh EXAMPLES
.Bd -literal -offset indent
newfs_hammer -L Home /dev/ad0s1d
.Ed
.Pp
Create a file system named
.Sq Home
on
.Pa /dev/ad0s1d .
.Sh DIAGNOSTICS
Exit status is 0 on success and 1 on error.
.Sh SEE ALSO
.Xr disklabel32 5 ,
.Xr disklabel64 5 ,
.Xr HAMMER 5 ,
.Xr fdisk 8 ,
.Xr gpt 8 ,
.Xr newfs 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Dx 1.11 .
.Sh AUTHORS
.An Matthew Dillon Aq dillon@backplane.com