in terms of our high-rate write load cassandra1.0.11 is about 3 (three!!) times slower than cassandra-0.7.8
after some investigation carried out I noticed files with "sha1" extension (which are missing for Cassandra-0.7.8)

in maybeWriteDigest() function I see no option fot switching sha1 digests off.

I agree, such digests save some network IO, but they seem to be very bad in terms of CPU and disk IO.
why to use one more digest (which have to be calculated), there's already relatively small Bloom filter file, which can be used for saving network traffic instead of sha1 digest.

any explanation ?

Ilya Shipitsin