Hi, I have Cassandra 0.6.6 running on 4 nodes with RF=2.
Let say nodes A, B, C, D If I have clients A1, B1, C1, D1 connected to respective nodes what happens when A1 requests A for a key "100" for which D is responsible as per the Token. C has the second copy. As per the logs A1 requests A which requests D and gets the data. D also checks a consistency check in the background on C. If I have RF=3 I assume D will do 2 consistency checks. If I need to get the data from A itself with minimum latency and network traversal between Data centers is this what I need to do ? 1. maybe RF=4 or at least >= 3 2. Adjust Read Consistency (ONE, QUORUM, DCQUORUM...) 3. Use RackAware strategy with DCQUORUM 3. Adjust Write Consistency Is there a way to get/write the data from the closest node - example A is in NY, D in London etc. For above example key=100. A1 calls A and A gets the data all the way from D. Also when A1 writes key=100 data needs to be written in D and C by A Probably need RF=4 for this in combination with DCQUORUM or ANY/ONE ? Want to know how everybody is approaching this cases ? A DEBUG [pool-1-thread-21] 2010-10-26 18:29:25,231 CassandraServer.java (line 216) get_slice DEBUG [pool-1-thread-21] 2010-10-26 18:29:25,231 StorageProxy.java (line 386) weakread reading SliceFromReadCommand(table='Keyspace1', key='100', column_parent='QueryPath(columnFamilyName='Standard2', superColumnName='null', columnName='null')', start='', finish='', reversed=true, count=1000000) from 1311748@/10.210.32.92 DEBUG [RESPONSE-STAGE:2] 2010-10-26 18:29:25,234 ResponseVerbHandler.java (line 52) Processing response on an async result from 1311748@/10.210.32.92 DEBUG [Timer-1] 2010-10-26 18:29:26,511 LoadDisseminator.java (line 36) Disseminating load info ... D DEBUG [ROW-READ-STAGE:5] 2010-10-26 18:29:19,415 SliceQueryFilter.java (line 116) collecting middle:false:1...@1288128381467000 DEBUG [ROW-READ-STAGE:5] 2010-10-26 18:29:19,415 SliceQueryFilter.java (line 116) collecting last:false:3...@1288128369639000 DEBUG [ROW-READ-STAGE:5] 2010-10-26 18:29:19,415 SliceQueryFilter.java (line 116) collecting first:false:4...@1288128358062000 DEBUG [ROW-READ-STAGE:5] 2010-10-26 18:29:19,415 ReadVerbHandler.java (line 93) Read key 100; sending response to 1311748@/10.210.32.74 DEBUG [CONSISTENCY-MANAGER:4] 2010-10-26 18:29:19,416 ConsistencyChecker.java (line 73) Reading consistency digest for 100 from 1081...@[/10.210.32.92, /10.210.32.93] DEBUG [RESPONSE-STAGE:1] 2010-10-26 18:29:19,418 ResponseVerbHandler.java (line 42) Processing response on a callback from 1081388@/10.210.32.93 C DEBUG [ROW-READ-STAGE:4] 2010-10-26 18:29:25,237 SliceQueryFilter.java (line 116) collecting middle:false:1...@1288128381467000 DEBUG [ROW-READ-STAGE:4] 2010-10-26 18:29:25,238 SliceQueryFilter.java (line 116) collecting last:false:3...@1288128369639000 DEBUG [ROW-READ-STAGE:4] 2010-10-26 18:29:25,238 SliceQueryFilter.java (line 116) collecting first:false:4...@1288128358062000 DEBUG [ROW-READ-STAGE:4] 2010-10-26 18:29:25,238 ReadVerbHandler.java (line 75) digest is c1ba97c56693d7fe4cbb9ac0544034b3 DEBUG [ROW-READ-STAGE:4] 2010-10-26 18:29:25,238 ReadVerbHandler.java (line 93) Read key 100; sending response to 1081388@/10.210.32.92
