I'm not convinced that 100KB is a great estimate on file size, but either way you're off by a few zeroes. It's not 270GB per day, it's 270TB. Even if each object were just one byte, that would be 2.7GB. 100KB is one hundred thousand bytes. So it's quite a bit more than eleven drives per day!
After applying the same shoddy math with each object being 100KB -- 270TB with 10 levels of redundancy across 3 RAID drives resulting in 8,100TB per day. This would be 8,100 drives (at 1TB per drive), or 8,910 drives after 10% being dead-on-arrival.
The math is sketchy, so let's cut it down by 10x (10KB per object): 891 drives per day. Keep in mind this is just for S3 and it doesn't account for existing drives failing, growth, or what other services require (eg: EC2, RDS, Cloudwatch, Cloudfront, etc).
