LVM LV Size Calculator
Calculate logical volume size allocation from available volume group extents.
Inputs
Feasibility
Feasible — 25600 extents allocated, 24400 extents remain free in the VG.
Actual LV Size After Rounding (GB)
100.0000
Extents Required
25,600
PE Rounding Waste (MB)
0.000
VG Free Extents After Allocation
24400
VG Free Capacity After (GB)
95.313
Step by step
Values used
VG Free Extents Available = 50,000; Physical Extent (PE) Size (MB) = 4; Requested LV Size (GB) = 100
LV size from extents
LV_size = extents × PE_size; can_extend = VG_free_extents ≥ requested_extents
Feasibility
= Feasible — 25600 extents allocated, 24400 extents remain free in the VG.
Actual LV Size After Rounding (GB)
= 100.0000
Extents Required
= 25,600
PE Rounding Waste (MB)
= 0.000
VG Free Extents After Allocation
= 24,400
VG Free Capacity After (GB)
= 95.31
How it works
A Logical Volume's actual size is always a whole number of Physical Extents (lvcreate rounds a requested size up to the nearest PE), and it can only be created or extended if the Volume Group has that many extents free. This calculator converts a requested LV size into extents, rounds up to the true allocated size, and checks feasibility against the VG's available free extents — the same math lvextend uses when growing an existing LV.
Formula
LV size from extents
LV_size = extents × PE_size; can_extend = VG_free_extents ≥ requested_extents
- e
- extents allocated
- P
- PE size
- E_free
- VG free extents
Frequently Asked Questions
Why is my LV slightly larger than what I requested?
lvcreate always allocates in whole Physical Extents, so a requested size that isn't an exact multiple of the PE size (commonly 4MB) gets rounded up to the next full extent — the difference is usually a few MB at most and is harmless.
What happens if I request more space than the VG has free?
lvcreate or lvextend will fail with an 'insufficient free space' error rather than partially allocating. You'd need to either request a smaller size, add another PV to the VG (vgextend), or free space by shrinking/removing another LV first.
Can an LV span multiple physical volumes?
Yes — by default LVM's linear mapping can allocate an LV's extents from any combination of PVs in the VG (contiguous per PV, but the LV as a whole can cross PV boundaries), which is how LVM lets a single logical volume exceed any one physical disk's size.