Hello Angyu,

unless a single client is present in the Vlan (for example a firewall) GLBP will attempt to load balance

you could configure router2 in such a way that it does not forward  (by tracking a non operational interface for example) but this would mean it will not be able to take over if the primary fails

see

http://www.cisco.com/en/US/docs/ios/ipapp/configuration/guide/ipapp_glbp_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1054488

otherwise you could with weighted load balancing algorythm have most of traffic on R1 and only a few on R2

maximum

Maximum weighting value in the range from 1 to 254. Default value is  100.

so you could configure 254 on R1, 10 on R2 and you could get 25:1 traffic ratio with  algorythm

glbp group load-balancing weighted

GLBP priority elects the AVG and weigthing decides how to load balance if using the above algorythm

you can consider to use VRRP if you want a standards based first hop redundancy protocol

see

http://www.cisco.com/en/US/docs/ios/ipapp/configuration/guide/ipapp_vrrp_ps6441_TSD_Products_Configuration_Guide_Chapter.html

Hope to help

Giuseppe