4.4.9. Extending a Striped Volume
In order to increase the size of a striped logical volume, there must be enough free space on the underlying physical volumes that make up the volume group to support the stripe. For example, if you have a two-way stripe that that uses up an entire volume group, adding a single physical volume to the volume group will not enable you to extend the stripe. Instead, you must add at least two physical volumes to the volume group.
For example, consider a volume group
vg that consists of two underlying physical volumes, as displayed with the following vgs command.
# vgs
VG #PV #LV #SN Attr VSize VFree
vg 2 0 0 wz--n- 271.31G 271.31G
You can create a stripe using the entire amount of space in the volume group.
#lvcreate -n stripe1 -L 271.31G -i 2 vgUsing default stripesize 64.00 KB Rounding up size to full physical extent 271.31 GB Logical volume "stripe1" created #lvs -a -o +devicesLV VG Attr LSize Origin Snap% Move Log Copy% Devices stripe1 vg -wi-a- 271.31G /dev/sda1(0),/dev/sdb1(0)
Note that the volume group now has no more free space.
# vgs
VG #PV #LV #SN Attr VSize VFree
vg 2 1 0 wz--n- 271.31G 0
The following command adds another physical volume to the volume group, which then has 135G of additional space.
# vgextend vg /dev/sdc1 Volume group "vg" successfully extended # vgs VG #PV #LV #SN Attr VSize VFree vg 3 1 0 wz--n- 406.97G 135.66G
At this point you cannot extend the striped logical volume to the full size of the volume group, because two underlying devices are needed in order to stripe the data.
# lvextend vg/stripe1 -L 406G
Using stripesize of last segment 64.00 KB
Extending logical volume stripe1 to 406.00 GB
Insufficient suitable allocatable extents for logical volume stripe1: 34480
more required
To extend the striped logical volume, add another physical volume and then extend the logical volume. In this example, having added two physical volumes to the volume group we can extend the logical volume to the full size of the volume group.
#vgextend vg /dev/sdd1Volume group "vg" successfully extended #vgsVG #PV #LV #SN Attr VSize VFree vg 4 1 0 wz--n- 542.62G 271.31G #lvextend vg/stripe1 -L 542GUsing stripesize of last segment 64.00 KB Extending logical volume stripe1 to 542.00 GB Logical volume stripe1 successfully resized
If you do not have enough underlying physical devices to extend the striped logical volume, it is possible to extend the volume anyway if it does not matter that the extension is not striped, which may result in uneven performance. When adding space to the logical volume, the default operation is to use the same striping parameters of the last segment of the existing logical volume, but you can override those parameters. The following example extends the existing striped logical volume to use the remaining free space after the initial
lvextend command fails.
#lvextend vg/stripe1 -L 406GUsing stripesize of last segment 64.00 KB Extending logical volume stripe1 to 406.00 GB Insufficient suitable allocatable extents for logical volume stripe1: 34480 more required #lvextend -i1 -l+100%FREE vg/stripe1
