[linux-lvm] Sparse LVs, --virtualsize equal to --size

[Alasdair G Kergon]

If you've got the capacity to test, create one that's quite a bit
larger and see how much space it actually uses up when full, then use
that size in future.  There's a header, and then the blocks are written
sequentially with an index block inserted ahead of each group of
data blocks.

Or try out thin LVs available in recent LVM releases/kernels for
an alternative 'sparse' approach.

Alasdair