So I have setup some test with Cassandra (with OCM). Though not very
impressed with the single read speeds , I have observed that it does scale
very well even with numerous number of concurrent readers .. However I have
observed that no matter what I do , I am somehow limitted to around 4 ms of
read per record .. I ran cfstats and noticed that one of the ColumnFamilies
(called Application) has the exact read latency that I have .. The other
ColumnFamily seems to be very good . You can see the cfstats output below.
Any reason why ..?
Read Count: 208678
Read Latency: 1.0831235635764191 ms.
Write Count: 0
Write Latency: NaN ms.
Pending Tasks: 0
Column Family: Server
SSTable count: 2
Space used (live): 43553650
Space used (total): 43553650
Memtable Columns Count: 0
Memtable Data Size: 0
Memtable Switch Count: 0
Read Count: 11200
Read Latency: 0.208 ms.
Write Count: 0
Write Latency: NaN ms.
Pending Tasks: 0
Key cache capacity: 200000
Key cache size: 1929
Key cache hit rate: 0.8369929601072745
Row cache: disabled
Compacted row minimum size: 0
Compacted row maximum size: 0
Compacted row mean size: 0
Column Family: Application
SSTable count: 1
Space used (live): 1816170
Space used (total): 1816170
Memtable Columns Count: 0
Memtable Data Size: 0
Memtable Switch Count: 0
Read Count: 43884
Read Latency: 4.051 ms.
Write Count: 0
Write Latency: NaN ms.
Pending Tasks: 0
Key cache capacity: 200000
Key cache size: 361
Key cache hit rate: 0.9917737672044481
Row cache: disabled
Compacted row minimum size: 0
Compacted row maximum size: 0
Compacted row mean size: 0
Column Family: BusinessUnit
SSTable count: 1
Space used (live): 4965
Space used (total): 4965
Memtable Columns Count: 0
Memtable Data Size: 0
Memtable Switch Count: 0
Read Count: 21942
Read Latency: 0.104 ms.
Write Count: 0
Write Latency: NaN ms.
Pending Tasks: 0
Key cache capacity: 200000
Key cache size: 13
Key cache hit rate: 0.999316379546076
Row cache: disabled
Compacted row minimum size: 0
Compacted row maximum size: 0
Compacted row mean size: 0
Column Family: Deployment
SSTable count: 1
Space used (live): 9694570
Space used (total): 9694570
Memtable Columns Count: 0
Memtable Data Size: 0
Memtable Switch Count: 0
Read Count: 43884
Read Latency: 0.526 ms.
Write Count: 0
Write Latency: NaN ms.
Pending Tasks: 0
Key cache capacity: 200000
Key cache size: 1018
Key cache hit rate: 0.9767796919150488
Row cache: disabled
Compacted row minimum size: 0
Compacted row maximum size: 0
Compacted row mean size: 0
Column Family: AppFamily
SSTable count: 1
Space used (live): 135233
Space used (total): 135233
Memtable Columns Count: 0
Memtable Data Size: 0
Memtable Switch Count: 0
Read Count: 43884
Read Latency: 0.344 ms.
Write Count: 0
Write Latency: NaN ms.
Pending Tasks: 0
Key cache capacity: 200000
Key cache size: 109
Key cache hit rate: 0.9975161790174095
Row cache: disabled
Compacted row minimum size: 0
Compacted row maximum size: 0
Compacted row mean size: 0
Column Family: SubBu
SSTable count: 1
Space used (live): 24659
Space used (total): 24659
Memtable Columns Count: 0
Memtable Data Size: 0
Memtable Switch Count: 0
Read Count: 43884
Read Latency: 0.125 ms.
Write Count: 0
Write Latency: NaN ms.
Pending Tasks: 0
Key cache capacity: 200000
Key cache size: 41
Key cache hit rate: 0.9990657187129706
Row cache: disabled
Compacted row minimum size: 0
Compacted row maximum size: 0
Compacted row mean size: 0
