chewychewy (6/3/2013)...
I supposed the above is when rebuilding online?
With the offline option, is it the same as above?
thanks
No, in both case space for a new copy of index is required.
ONLINE = you can perform DML on the underlying table. OFFLINE = you can't perform DML on the underlying table.
For lowering log space usage (log backup size will be almost the same) you can consider the Bulk-Logged recovery mode, but first read about bulk-logged recovery mode.