Use metas for LUNs requiring high performance (thousands of IOPs).  If the performance requirements are not that high, a single LUN is fine.

Or if you are putting LUNs together in a host stripe, you shouldn't need meta volumes either.

You can create 100 GB single lun .it's not an issue for performance .But if you create big single  lun ,it might be an issue for performance.

While creating me volume u must match ---

1> disk speed should be same for both lun.

2>if possible ,RAID also can be same.

3>make sure its stripe not concatenation

then there will not be any issue for performance for meta lun.

There typically is some IOP to GB ratio, so a larger LUN is likely to have more IOP demand, but a small LUN COULD have a higher IOP demand than a large LUN.