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From aaron morton <aa...@thelastpickle.com>
Subject Re: Single node cassandra
Date Wed, 24 Aug 2011 09:51:12 GMT
I would get an idea of how this one node is performing. When you put it under load is the latency
ok ? Is it read or write heavy? When it's write heavy does it flush to disk more frequently
because there is not a lot of memory for the Memtables? 

Without thinking to hard I would say move to the 16GB nodes (that seems to be the sweet spot)
if you started OOM'ing or seeing GC slow your down. And the next step would be move to more
nodes :) Here is some more info http://thelastpickle.com/2011/05/04/How-are-Memtables-measured/

If it's inside your current needs stick with what you have. You can then online upgrade or
take the pain and to a stop+copy upgrade to a new machine pretty easily. 

Hope that helps. 

-----------------
Aaron Morton
Freelance Cassandra Developer
@aaronmorton
http://www.thelastpickle.com

On 24/08/2011, at 1:52 PM, Derek Andree wrote:

> I'm looking for advice for running cassandra 8.+ on a single node.   Would love to hear
stories about how much RAM you succeeded with, etc.
> 
> Currently we are running with a 4GB heap size.  Hardware is 4 cores and 8GB physical
memory.  We're not opposed to going to 16GB of memory or even 32GB.  We have fast 6GBps SAS
drives, although currently do not have a dedicated drive for Commit Log, but we are thinking
about trying this out.
> 
> Our application has time series data which means our data will get larger over time,
not in all CFs though.  We have 7 "hot" CFs but they are probably not that hot to someone
running a sizable cluster.  We have 15 CFs total in our keyspace.
> 
> I've already tweaked key cache and in some cases added a large enough row cache to keep
an entire CF in memory where appropriate.
> 
> Basically, I'm just curious under this sort of load if we can expect decent results with
a single node as the data gets larger.  I know this isn't necessarily a binary answer, just
curious about people's experiences on a single node.
> 
> 
> Thanks,
> -Derek
> 
> 
> cfstats:
> 
> 
> ----------------
> 	Keyspace: test
> 	Read Count: 2869777
> 	Read Latency: 1.2266526890416922 ms.
> 	Write Count: 7672036
> 	Write Latency: 0.016663120975970395 ms.
> 	Pending Tasks: 0
> 		Column Family: DocData
> 		SSTable count: 1
> 		Space used (live): 425090
> 		Space used (total): 425090
> 		Number of Keys (estimate): 128
> 		Memtable Columns Count: 0
> 		Memtable Data Size: 0
> 		Memtable Switch Count: 0
> 		Read Count: 162
> 		Read Latency: NaN ms.
> 		Write Count: 0
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 1000
> 		Key cache size: 27
> 		Key cache hit rate: NaN
> 		Row cache: disabled
> 		Compacted row minimum size: 771
> 		Compacted row maximum size: 315852
> 		Compacted row mean size: 18290
> 
> 		Column Family: User
> 		SSTable count: 1
> 		Space used (live): 5368
> 		Space used (total): 5368
> 		Number of Keys (estimate): 128
> 		Memtable Columns Count: 0
> 		Memtable Data Size: 0
> 		Memtable Switch Count: 0
> 		Read Count: 0
> 		Read Latency: NaN ms.
> 		Write Count: 0
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 1000
> 		Key cache size: 0
> 		Key cache hit rate: NaN
> 		Row cache capacity: 1000
> 		Row cache size: 0
> 		Row cache hit rate: NaN
> 		Compacted row minimum size: 447
> 		Compacted row maximum size: 535
> 		Compacted row mean size: 535
> 
> 		Column Family: SMapping
> 		SSTable count: 1
> 		Space used (live): 536900
> 		Space used (total): 536900
> 		Number of Keys (estimate): 768
> 		Memtable Columns Count: 9528
> 		Memtable Data Size: 4646940
> 		Memtable Switch Count: 0
> 		Read Count: 763
> 		Read Latency: NaN ms.
> 		Write Count: 763
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 1000
> 		Key cache size: 763
> 		Key cache hit rate: NaN
> 		Row cache capacity: 1000
> 		Row cache size: 763
> 		Row cache hit rate: NaN
> 		Compacted row minimum size: 447
> 		Compacted row maximum size: 73457
> 		Compacted row mean size: 713
> 
> 		Column Family: LObject
> 		SSTable count: 2
> 		Space used (live): 6945430
> 		Space used (total): 6945430
> 		Number of Keys (estimate): 10752
> 		Memtable Columns Count: 729638
> 		Memtable Data Size: 400799230
> 		Memtable Switch Count: 2
> 		Read Count: 316756
> 		Read Latency: NaN ms.
> 		Write Count: 147028
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 20000
> 		Key cache size: 20000
> 		Key cache hit rate: NaN
> 		Row cache capacity: 20000
> 		Row cache size: 5304
> 		Row cache hit rate: NaN
> 		Compacted row minimum size: 259
> 		Compacted row maximum size: 182785
> 		Compacted row mean size: 661
> 
> 		Column Family: SMeta
> 		SSTable count: 2
> 		Space used (live): 173059487
> 		Space used (total): 343520951
> 		Number of Keys (estimate): 165760
> 		Memtable Columns Count: 442764
> 		Memtable Data Size: 168300272
> 		Memtable Switch Count: 53
> 		Read Count: 2345765
> 		Read Latency: 0.009 ms.
> 		Write Count: 2179885
> 		Write Latency: 0.033 ms.
> 		Pending Tasks: 0
> 		Key cache: disabled
> 		Row cache capacity: 100000
> 		Row cache size: 82940
> 		Row cache hit rate: 1.0
> 		Compacted row minimum size: 925
> 		Compacted row maximum size: 1109
> 		Compacted row mean size: 1109
> 
> 		Column Family: SLookback
> 		SSTable count: 14
> 		Space used (live): 16604796474
> 		Space used (total): 17754314562
> 		Number of Keys (estimate): 2515968
> 		Memtable Columns Count: 49500
> 		Memtable Data Size: 38927091
> 		Memtable Switch Count: 18
> 		Read Count: 194587
> 		Read Latency: 13.929 ms.
> 		Write Count: 200732
> 		Write Latency: 0.011 ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 200000
> 		Key cache size: 200000
> 		Key cache hit rate: 0.2599537318884695
> 		Row cache: disabled
> 		Compacted row minimum size: 311
> 		Compacted row maximum size: 35425
> 		Compacted row mean size: 7338
> 
> 		Column Family: Event
> 		SSTable count: 2
> 		Space used (live): 23480776
> 		Space used (total): 23480776
> 		Number of Keys (estimate): 33280
> 		Memtable Columns Count: 77
> 		Memtable Data Size: 5310
> 		Memtable Switch Count: 1
> 		Read Count: 12
> 		Read Latency: NaN ms.
> 		Write Count: 12
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 10000
> 		Key cache size: 0
> 		Key cache hit rate: NaN
> 		Row cache capacity: 1000
> 		Row cache size: 0
> 		Row cache hit rate: NaN
> 		Compacted row minimum size: 643
> 		Compacted row maximum size: 770
> 		Compacted row mean size: 770
> 
> 		Column Family: SHourly
> 		SSTable count: 3
> 		Space used (live): 847441284
> 		Space used (total): 847441284
> 		Number of Keys (estimate): 496768
> 		Memtable Columns Count: 35256
> 		Memtable Data Size: 67814381
> 		Memtable Switch Count: 3
> 		Read Count: 0
> 		Read Latency: NaN ms.
> 		Write Count: 330520
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 1000
> 		Key cache size: 0
> 		Key cache hit rate: NaN
> 		Row cache: disabled
> 		Compacted row minimum size: 180
> 		Compacted row maximum size: 9887
> 		Compacted row mean size: 1835
> 
> 		Column Family: ConfigSettings
> 		SSTable count: 1
> 		Space used (live): 4854
> 		Space used (total): 4854
> 		Number of Keys (estimate): 128
> 		Memtable Columns Count: 0
> 		Memtable Data Size: 0
> 		Memtable Switch Count: 0
> 		Read Count: 135
> 		Read Latency: 0.007 ms.
> 		Write Count: 0
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 100
> 		Key cache size: 1
> 		Key cache hit rate: NaN
> 		Row cache capacity: 100
> 		Row cache size: 1
> 		Row cache hit rate: 1.0
> 		Compacted row minimum size: 536
> 		Compacted row maximum size: 642
> 		Compacted row mean size: 642
> 
> 		Column Family: SystemMeta
> 		SSTable count: 2
> 		Space used (live): 9258
> 		Space used (total): 9258
> 		Number of Keys (estimate): 256
> 		Memtable Columns Count: 48
> 		Memtable Data Size: 2570
> 		Memtable Switch Count: 1
> 		Read Count: 18
> 		Read Latency: NaN ms.
> 		Write Count: 10
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 100
> 		Key cache size: 1
> 		Key cache hit rate: NaN
> 		Row cache capacity: 100
> 		Row cache size: 1
> 		Row cache hit rate: NaN
> 		Compacted row minimum size: 311
> 		Compacted row maximum size: 372
> 		Compacted row mean size: 372
> 
> 		Column Family: LConfig
> 		SSTable count: 2
> 		Space used (live): 22198
> 		Space used (total): 22198
> 		Number of Keys (estimate): 256
> 		Memtable Columns Count: 3614
> 		Memtable Data Size: 399019
> 		Memtable Switch Count: 1
> 		Read Count: 261
> 		Read Latency: NaN ms.
> 		Write Count: 261
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 1000
> 		Key cache size: 9
> 		Key cache hit rate: 0.0
> 		Row cache capacity: 1000
> 		Row cache size: 9
> 		Row cache hit rate: NaN
> 		Compacted row minimum size: 643
> 		Compacted row maximum size: 770
> 		Compacted row mean size: 770
> 
> 		Column Family: S
> 		SSTable count: 6
> 		Space used (live): 4845200284
> 		Space used (total): 4926197540
> 		Number of Keys (estimate): 496512
> 		Memtable Columns Count: 61093
> 		Memtable Data Size: 116164716
> 		Memtable Switch Count: 26
> 		Read Count: 11318
> 		Read Latency: 76.083 ms.
> 		Write Count: 2215986
> 		Write Latency: 0.008 ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 5000
> 		Key cache size: 5000
> 		Key cache hit rate: 0.0018995517057974318
> 		Row cache: disabled
> 		Compacted row minimum size: 216
> 		Compacted row maximum size: 105778
> 		Compacted row mean size: 10079
> 
> 		Column Family: SLookbackLog
> 		SSTable count: 2
> 		Space used (live): 23988670
> 		Space used (total): 23988670
> 		Number of Keys (estimate): 10496
> 		Memtable Columns Count: 111401
> 		Memtable Data Size: 50531214
> 		Memtable Switch Count: 7
> 		Read Count: 0
> 		Read Latency: NaN ms.
> 		Write Count: 2431579
> 		Write Latency: 0.007 ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 10496
> 		Key cache size: 0
> 		Key cache hit rate: NaN
> 		Row cache capacity: 10496
> 		Row cache size: 0
> 		Row cache hit rate: NaN
> 		Compacted row minimum size: 73
> 		Compacted row maximum size: 20501
> 		Compacted row mean size: 2484
> 
> 		Column Family: Tag
> 		SSTable count: 0
> 		Space used (live): 0
> 		Space used (total): 0
> 		Number of Keys (estimate): 0
> 		Memtable Columns Count: 0
> 		Memtable Data Size: 0
> 		Memtable Switch Count: 0
> 		Read Count: 0
> 		Read Latency: NaN ms.
> 		Write Count: 0
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 1000
> 		Key cache size: 0
> 		Key cache hit rate: NaN
> 		Row cache capacity: 1000
> 		Row cache size: 0
> 		Row cache hit rate: NaN
> 		Compacted row minimum size: 0
> 		Compacted row maximum size: 0
> 		Compacted row mean size: 0
> 
> 		Column Family: SDaily
> 		SSTable count: 1
> 		Space used (live): 60375798
> 		Space used (total): 60375798
> 		Number of Keys (estimate): 166016
> 		Memtable Columns Count: 165260
> 		Memtable Data Size: 8056425
> 		Memtable Switch Count: 0
> 		Read Count: 0
> 		Read Latency: NaN ms.
> 		Write Count: 165260
> 		Write Latency: NaN ms.
> 		Pending Tasks: 0
> 		Key cache capacity: 1000
> 		Key cache size: 0
> 		Key cache hit rate: NaN
> 		Row cache: disabled
> 		Compacted row minimum size: 150
> 		Compacted row maximum size: 446
> 		Compacted row mean size: 284
> 
> ----------------
> 


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