Database Reference
In-Depth Information
Common Problems
Some common Cassandra problems already have well-defined solutions that you
can try. Here, we have included some of the more common problems that are seen
by Cassandra users as well as some of the possible solutions. Your mileage may
vary.
Slow Reads, Fast Writes
One of the most common problems of a schema that is not properly set up is that
you start to see your reads slowing down and your write speeds staying consistent
(or at least not slowing down in comparison to the reads).
Listing 10.4
shows an
example of
cfstats
output with high read latency.
Listing 10.4
cfstats
Output with a High Read Latency
# nodetool cfstats | grep -A 19 events_2013_06
Column Family: events_2013_06
SSTable count: 4
Space used (live): 26422246080
Space used (total): 26422246080
Number of Keys (estimate): 11566336
Memtable Columns Count: 46240
Memtable Data Size: 79644540
Memtable Switch Count: 1116
Read Count: 7867823
Read Latency: 185.175 ms.
Write Count: 170267477
Write Latency: 0.025 ms.
Pending Tasks: 3
Bloom Filter False Positives: 0
Bloom Filter False Ratio: 0.00000
Bloom Filter Space Used: 25018624
Compacted row minimum size: 373
Compacted row maximum size: 962624926
Compacted row mean size: 18170
