Data transfer from Disk to Memory too slow

Hi ,

i am wokring on a project for BW on HANA and the past two days we have run some performance test.

We run the Queries from BW (large Data) and we noticed that, when the data are already loaded in memory  the Query result ist faster and thus i have some questions:

1. Why take so long to transfer the data from diks to memory?
   Query time with preload of data in memory : 10 sec
   Query time with initial data in Disk : more than 600 sec
   (in some other cases the discrepancy was larger)
   Also the statement LOAD <table name> from HANA Studio takes too long.
2. Are the Data in Disk uncompressed ?
   Because i notice the used storage in Disk is too high (almost 500GB, All of the BW tables are ~250 GB)
3. When and how will be pushed the unused data from Memory to disk ?
   For example: I have an InfoCube with data for the past 3 years, but in the query i use often only the last year. Would be pushed the data partially away   from momery?
4. Where can i see the Compression rate of my data?

Thank you in advance & regards,

Vjola