My advice, don't wait to back up your data to any device you can, don't wait until you have money to buy an external drive and when you do get an external drive, don't put all your faith in it as it is only a single drive itself and can also fail! I have had a 1TB drive fail on me...
If storage is a problem then cloud storage is one answer, Google, Yahoo (I understand they have up to 1TB of email space, emailing yourself is one way of saving images) use services like Flickr and also One Drive from M$ gives you a few Gigs of storage space.
As for backing up your drive in its entirety the
dd command I got working, tried the suggested
cat command to copy the failing drive, eventually I was able to save one drive but my ASUS laptop HDD has taken the whole PC down as it won't go in to BIOS until its detected the HDD!!!
dd if=/dev/<your drive to copy> | gzip -c > /<mount point>/<folder>/imageName.gz
and my 64 GB drive took 10 Hours to compress in to a compressed image, IMHO if you have the drive space, don't bother compressing, just store, it will be quicker and I only saved 10GiB in doing compression.
I haven't restored an image as yet, I only need a copy of the drive as my next step may wreck the partitions completely, hence the need of a back up image...
Hope this helps.