you're probably reading more or larger columns from that CF.
I would consider using row cache on that CF and on Deployment based on
the query volumes seen here.
On Fri, Jun 11, 2010 at 12:32 PM, Nazario Parsacala
<dodongjuan@gmail.com> wrote:
> 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
>
--
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support
http://riptano.com
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