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During updates, HBase and Cassandra went far ahead from the main group with the average response latency time not exceeding two milliseconds. HBase was even faster. HBase client was configured with AutoFlush turned off. The updates aggregated in the client buffer and pending writes flushed asynchronously, as soon as the buffer became full. To accelerate updates processing on the server, the deferred log flush was enabled and WAL edits were kept in memory during the flush period.
Cassandra wrote the mutation to the commit log for the transaction purposes and then an in-memory Memtable was updated. This is a slower, but safer scenario if compared to the HBase deferred log flushing.
* Workload A: Read. During reads, per-column family compression provides HBase and Cassandra with faster data access. HBase was configured with native LZO and Cassandra with Google's Snappy compression codecs. Although the computation ran longer, the compression reduces the number of bytes read from the disk.
* Workload B: Read-heavy mode. Workload B consisted of 95% of reads and 5% of writes. Content tagging can serve as an example task matching this workload;
adding a tag is an update, but most operations imply reading tags. Settings for the "read-mostly" workload:
1) Read/update ratio: 95/5
2) Zipfian request distribution