[CentOS] space problem

CentOS 6.2. I have a 2TB drive, one partition, which is used for online
backups. It filled up the other day. I moved a couple of b/u directories
off it, and deleted the originals, which should have given me 42G free. I
also reduced the reserved blocks by 1/3rd.

I've just finished an fsck, which it needed anyway, and in which there was
a problem in an HTREE directory node.

df *still* tells me that there are zero bytes free.

Clues?

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