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Cassandra, very long row (over 800.000 columns), row cache and manual repair

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http://serverfault.com – I seemed to have hit quite interesting problem recently while investigating my previous problem -- One ColumnFamily places data on only 3 out of 4 nodes We had a very long row with over 800.000 columns in it. It stored user details; one column per one user's details. Not getting in reasons behind this kind of designs, according to documentation this should be fine, however we were having massive performance problems. It seemed as the whole row was cache by the operating system cache and Cassandra -- because it was fairly often used row -- was spending most of the CPU time on serialising th (HowTos)