cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Read latency on one ColumnFamily greater than the rest of Column Families ..
Date Fri, 11 Jun 2010 20:53:55 GMT
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
Mime
View raw message