I backed up the blockchain data recently (late October) it was 160GB uncompressed, I used 7zip with normal compression and it is 112GB in 25 dvd sized archive files.
Data compression;
When data compression is used in a data transmission application,the goal is speed. Speed of transmission depends upon the number of bits sent,the time required for the encoder to generate the coded message and the time required for the decoder to recover the original ensemble. In a data storage application,Although the degree of compression is the primary concern,it is nonetheless necessary that the algorithm be efficient in order for the scheme to be practical.
As discussed in the Introduction,data compression has wide application in terms of information storage,including representation of the abstract data type string and file compression.Huffman coding is used for compression in several file archival systems [ARC 1986; one of the adaptive schemes to be discussed in Section 5.An adaptive Huffman coding technique is the basis for the compact command of the UNIX operating system.
one could expect to see even greater use of variable-length coding in the future.