Cassandra writes are particularly fast, for a few reasons:
1) Most writes go to a commitlog (append-only file, written linearly, so particularly fast in terms of disk operations) and then pushed to the memTable. Memtable is flushed in batches to the permanent data files, so it buffers many mutations and then does a sequential write to persist that data to disk. 2) Reads may have to merge data from many data tables on disk. Because the writes (described very briefly in step 1) write to immutable files, updates/deletes have to be merged on read – this is extra effort for the read path. If you don’t do much in terms of overwrites/deletes, and your partitions are particularly small, and your data fits in RAM (probably mmap/page cache of data files, unless you’re using the row cache), reads may be very fast for you. Certainly individual reads on low-merge workloads can be < 0.1ms. - Jeff From: Vikas Jaiman <er.vikasjai...@gmail.com> Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org> Date: Sunday, November 6, 2016 at 12:42 PM To: "user@cassandra.apache.org" <user@cassandra.apache.org> Subject: Are Cassandra writes are faster than reads? Hi all, Are Cassandra writes are faster than reads ?? If yes, why is this so? I am using consistency 1 and data is in memory. Vikas
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