sstable count=0, why nodetool ring is not 0

[祝海通]

hi,all

We are using Cassandra 1.0.2. I am testing the TTL with loading 400G.
When all the data are expired, I waited for some hours.
Later, the nodetool ring is still have 90GB. So I made a major compaction.
Then there are 30GB from the nodetool ring. After I saw the file system,I
found there are zero sstable.
I don't know where comes the 30GB?

Best Regards