Dne 25.12.2011 20:58, Peter Schuller napsal(a):
Read Count: 68844
[snip]
why reported bloom filter FP ratio is not counted like this
10/68844.0
0.00014525594096798558
Because the read count is total amount of reads to the CF, while the
bloom filter is per sstable. The number of individual reads to
sstables will be higher than the number of reads to the CF (unless you
happen to have exactly one sstable or no rows ever span sstables).
but reported ratio is Bloom Filter False Ratio: 0.00495 which is higher
than my computed ratio 0.000145. If you were true than reported ratio
should be lower then mine computed from CF reads because there are more
reads to sstables then to CF.
from investigation of bloom filter FP ratio it seems that default bloom
filter FP ratio (soon user configurable) should be higher. Hbase
defaults to 1% cassandra defaults to 0.000744. bloom filters are using
quite a bit memory now.
