On 17/02/2012 8:53 AM, "Eran Chinthaka Withana" <eran.chinth...@gmail.com> wrote: > > Hi Jonathan, > > Thanks for the reply. Yes there is a possibility that the keys can be distributed in multiple SSTables, but my data access patterns are such that I always read/write the whole row. So I expect all the data to be in the same SSTable (please correct me if I'm wrong). > > For some reason 16637958 (the keys cached) has become a golden number and I don't see key cache increasing beyond that. I also checked memory and I have about 4GB left in JVM memory and didn't see any issues on logs.
I have seen the same thing with the keycache size becoming static cheers > > Thanks, > Eran Chinthaka Withana > > > > On Thu, Feb 16, 2012 at 1:20 PM, Jonathan Ellis <jbel...@gmail.com> wrote: >> >> So, you have roughly 1/6 of your (physical) row keys cached and about >> 1/4 cache hit rate, which doesn't sound unreasonable to me. Remember, >> each logical key may be spread across multiple physical sstables -- >> each (key, sstable) pair is one entry in the key cache. >> >> On Thu, Feb 16, 2012 at 1:48 PM, Eran Chinthaka Withana >> <eran.chinth...@gmail.com> wrote: >> > Hi Aaron, >> > >> > Here it is. >> > >> > Keyspace: XXXX >> > Read Count: 1123637972 >> > Read Latency: 5.757938114343114 ms. >> > Write Count: 128201833 >> > Write Latency: 0.0682576607387509 ms. >> > Pending Tasks: 0 >> > Column Family: YY >> > SSTable count: 18 >> > Space used (live): 103318720685 >> > Space used (total): 103318720685 >> > Number of Keys (estimate): 92404992 >> > Memtable Columns Count: 1425580 >> > Memtable Data Size: 359655747 >> > Memtable Switch Count: 2522 >> > Read Count: 1123637972 >> > Read Latency: 14.731 ms. >> > Write Count: 128201833 >> > Write Latency: NaN ms. >> > Pending Tasks: 0 >> > Bloom Filter False Postives: 1488 >> > Bloom Filter False Ratio: 0.00000 >> > Bloom Filter Space Used: 331522920 >> > Key cache capacity: 16637958 >> > Key cache size: 16637958 >> > Key cache hit rate: 0.2708333333333333 >> > Row cache: disabled >> > Compacted row minimum size: 51 >> > Compacted row maximum size: 6866 >> > Compacted row mean size: 2560 >> > >> > Thanks, >> > Eran Chinthaka Withana >> > >> > >> > >> > On Thu, Feb 16, 2012 at 12:30 AM, aaron morton <aa...@thelastpickle.com > >> > wrote: >> >> >> >> Its in the order of 261 to 8000 and the ratio is 0.00. But i guess 8000 is >> >> bit high. Is there a way to fix/improve it? >> >> >> >> Sorry I don't understand what you mean. But if the ratio is 0.0 all is >> >> good. >> >> >> >> Could you include the full output from cfstats for the CF you are looking >> >> at ? >> >> >> >> Cheers >> >> >> >> ----------------- >> >> Aaron Morton >> >> Freelance Developer >> >> @aaronmorton >> >> http://www.thelastpickle.com >> >> >> >> On 15/02/2012, at 1:00 PM, Eran Chinthaka Withana wrote: >> >> >> >> Its in the order of 261 to 8000 and the ratio is 0.00. But i guess 8000 is >> >> bit high. Is there a way to fix/improve it? >> >> >> >> Thanks, >> >> Eran Chinthaka Withana >> >> >> >> >> >> On Tue, Feb 14, 2012 at 3:42 PM, aaron morton <aa...@thelastpickle.com > >> >> wrote: >> >>> >> >>> Out of interest what does cfstats say about the bloom filter stats ? A >> >>> high false positive could lead to a low key cache hit rate. >> >>> >> >>> Also, is there a way to warm start the key cache, meaning pre-load the >> >>> amount of keys I set as keys_cached? >> >>> >> >>> See key_cache_save_period when creating the CF. >> >>> >> >>> Cheers >> >>> >> >>> >> >>> ----------------- >> >>> Aaron Morton >> >>> Freelance Developer >> >>> @aaronmorton >> >>> http://www.thelastpickle.com >> >>> >> >>> On 15/02/2012, at 5:54 AM, Eran Chinthaka Withana wrote: >> >>> >> >>> Hi, >> >>> >> >>> I'm using Cassandra 1.0.7 and I've set the keys_cached to about 80% >> >>> (using the numerical values). This is visible in cfstats too. But I'm >> >>> getting less than 20% (or sometimes even 0%) key cache hit rate. Well, the >> >>> data access pattern is not the issue here as I know they are retrieving the >> >>> same row multiple times. I'm using hector client with dynamic load balancing >> >>> policy with consistency ONE for both reads and writes. Any ideas on how to >> >>> find the issue and fix this? >> >>> >> >>> Here is what I see on cfstats. >> >>> >> >>> Key cache capacity: 16637958 >> >>> Key cache size: 16637958 >> >>> Key cache hit rate: 0.045454545454545456 >> >>> >> >>> Also, is there a way to warm start the key cache, meaning pre-load the >> >>> amount of keys I set as keys_cached? >> >>> >> >>> Thanks, >> >>> Eran >> >>> >> >>> >> >> >> >> >> > >> >> >> >> -- >> Jonathan Ellis >> Project Chair, Apache Cassandra >> co-founder of DataStax, the source for professional Cassandra support >> http://www.datastax.com > >
