Why so?
What are pluses and minuses?
As for me, I am looking for number of files in directory.
700GB/512MB*5(files per SST) = 7000 files, that is OK from my view.
700GB/5MB*5 = 700000 files, that is too much for single directory, too much memory used for SST data, toohuge compaction queue (that leads to strange pauses, I suppose because of compactor thinking what to compact next),...

2012/9/23 Aaron Turner <synfinatic@gmail.com>
On Sun, Sep 23, 2012 at 8:18 PM, ̦ <tivv00@gmail.com> wrote:
> If you think about space, use Leveled compaction! This won't only allow you
> to fill more space, but also will shrink you data much faster in case of
> updates. Size compaction can give you 3x-4x more space used than there are
> live data. Consider the following (our simplified) scenario:
> 1) The data is updated weekly
> 2) Each week a large SSTable is written (say, 300GB) after full update
> processing.
> 3) In 3 weeks you will have 1.2TB of data in 3 large SSTables.
> 4) Only after 4th week they all will be compacted into one 300GB SSTable.
> Leveled compaction've tamed space for us. Note that you should set
> sstable_size_in_mb to reasonably high value (it is 512 for us with ~700GB
> per node) to prevent creating a lot of small files.

512MB per sstable? Wow, that's freaking huge. From my conversations
with various developers 5-10MB seems far more reasonable. I guess it
really depends on your usage patterns, but that seems excessive to me-
especially as sstables are promoted.

Best regards,
Vitalii Tymchyshyn