[Qgis-user] Pyramids and Virtual maps

[Zirneklitis]

Hi,

I have many raster maps (size 2000x2000 pixels). I have created a 
virtual dataset including all of them.

The first question: what pyramids should be built?

1. Large scale pyramids (e.g. 2 and 8) for each raster map separately 
and small scale pyramids (e.g. 16 and 32) for the Virtual data set.

OR

2. Full set of pyramids for the Virtual data set.


The second question:  Is it reasonable to make only every second pyramid 
(e.g. 4, 16, 64)? - performance/disk waste issue.

Thank You,
Karlis