Friday, September 26, 2014
Saturday, September 13, 2014
(I am yet to try this)
Apparently setting the min/max threshold value to 0 stops the compaction. Also, this is only possible from JMX and not from CLI!
Another option is to use 'disableautocompaction' using "nodetool disableautocompaction"
Yet to verify this.
Friday, September 12, 2014
- Size tiered compaction
- Level tiered compaction
Size Tiered CompactionIn this compaction process, SSTables of fixed size are created initially and ones the number of SSTables reach a threshold count, they are compacted into a bigger SSTable.
Level Tiered CompactionIn this compaction process, sstables of a fixed, relatively small size (5MB by default in Cassandra’s implementation) are created and grouped into “levels”. Within each level, sstables are guaranteed to be non-overlapping. Each level is ten times as large as the previous.
Comparison at high level
- Size Tiered compaction is better suited for write heavy applications. As the sstables are not immediately compacted with next level, the write performance will be better.
- For column families having very wide rows with frequent updates (for example, manual index rows) the read performance will be severely hit. I have observed a case where a single read accessed almost 800 SSTables for a column family with wide row containing more than a million columns – case of frequent readTimeOuts! (This is also a learning for Data Model design and explains why wide rows with millions of columns should be avoided!)
- Level Tiered compaction is better suited for column families with heavy read operations and/or heavy update-operations! (Important: Different between a write and an update!)
Thursday, September 4, 2014
jinfo [option] <pid>
(to connect to running process)
jinfo [option] <executable <core>
(to connect to a core file)
jinfo [option] [server_id@]<remote server IP or hostname>
(to connect to remote debug server)
where <option> is one of:
-flag <name> to print the value of the named VM flag
-flag [+|-]<name> to enable or disable the named VM flag
-flag <name>=<value> to set the named VM flag to the given value
-flags to print VM flags
-sysprops to print Java system properties
<no option> to print both of the above
-h | -help to print this help message