Pieces tab

From AzureusWiki

If you double-click a torrent that is still downloading you will see the Pieces tab.

The column Type in there shows Slow or Fast. Slow/fast is the categorisation of the peers that contribute to this piece. This was introduced in Azureus in order to limit the effect of "1 small block from a slow peer is blocking the piece completion". So all the slow peers contribute to "slow" pieces, and all the "fast" peers contribute to fast pieces. It helps keeping the number of concurrent pieces low, and so, the cache effect.

The limit is at about 2kB/s, so it's really to avoid "blocking peers" from blocking pieces.

Read the Azureus FAQ