5.4.2. Creating Striped Volumes
For large sequential reads and writes, creating a striped logical volume can improve the efficiency of the data I/O. For general information about striped volumes, see Section 3.3.2, “Striped Logical Volumes”.
When you create a striped logical volume, you specify the number of stripes with the
-iargument of the
lvcreatecommand. This determines over how many physical volumes the logical volume will be striped. The number of stripes cannot be greater than the number of physical volumes in the volume group (unless the
--alloc anywhereargument is used).
If the underlying physical devices that make up a striped logical volume are different sizes, the maximum size of the striped volume is determined by the smallest underlying device. For example, in a two-legged stripe, the maximum size is twice the size of the smaller device. In a three-legged stripe, the maximum size is three times the size of the smallest device.
The following command creates a striped logical volume across 2 physical volumes with a stripe of 64kB. The logical volume is 50 gigabytes in size, is named
gfslv, and is carved out of volume group
lvcreate -L 50G -i2 -I64 -n gfslv vg0
As with linear volumes, you can specify the extents of the physical volume that you are using for the stripe. The following command creates a striped volume 100 extents in size that stripes across two physical volumes, is named
stripelvand is in volume group
testvg. The stripe will use sectors 0-49 of
/dev/sda1and sectors 50-99 of
lvcreate -l 100 -i2 -nstripelv testvg /dev/sda1:0-49 /dev/sdb1:50-99Using default stripesize 64.00 KB Logical volume "stripelv" created