Striping is a method used to combine several disk drives into a single volume. In many cases, this is done through the use of hardware controllers. The GEOM disk subsystem provides software support for RAID0, also known as disk striping.
In a RAID0 system, data are split up in blocks that get written across all the drives in the array. Instead of having to wait on the system to write 256k to one disk, a RAID0 system can simultaneously write 64k to each of four different disks, offering superior I/O performance. This performance can be enhanced further by using multiple disk controllers.
Each disk in a RAID0 stripe must be of the same size, since I/O requests are interleaved to read or write to multiple disks in parallel.
Load the geom_stripe
module:
#
kldload geom_stripe.ko
Ensure that a suitable mount point exists. If this
volume will become a root partition, then temporarily use
another mount point such as /mnt
:
#
mkdir /mnt
Determine the device names for the disks which will
be striped, and create the new stripe device. For example,
the following command could be used to stripe two unused,
unpartitioned ATA disks:
/dev/ad2
and
/dev/ad3
.
#
gstripe label -v st0 /dev/ad2 /dev/ad3
A partition table must be created on the new volume with the following command:
#
bsdlabel -wB /dev/stripe/st0
This process should have created two other devices
in the /dev/stripe
directory in addition to the st0
device.
Those include st0a
and
st0c
. A file system must now be created
on the st0a
device using the following
newfs
command:
#
newfs -U /dev/stripe/st0a
Many numbers will glide across the screen, and after a few seconds, the process will be complete. The volume has been created and is ready to be mounted.
The following command can be used to manually mount a newly created disk stripe:
#
mount /dev/stripe/st0a /mnt
To mount this striped file system automatically during the boot
process, place the volume information in
/etc/fstab
file:
#
echo "/dev/stripe/st0a /mnt ufs rw 2 2" \
>> /etc/fstab
The geom_stripe
module must also be automatically loaded during
system initialization, by adding a line to
/boot/loader.conf
:
#
echo 'geom_stripe_load="YES"' >> /boot/loader.conf
All FreeBSD documents are available for download at https://download.freebsd.org/ftp/doc/
Questions that are not answered by the
documentation may be
sent to <freebsd-questions@FreeBSD.org>.
Send questions about this document to <freebsd-doc@FreeBSD.org>.