Re: LCS Strategy, compaction pending tasks keep increasing

Reads are mostly limited by IO so I’d set concurrent_read to something related to your disks, we have set it to 64 (yet we have SSDs) Writes are mostly limited by CPU, so the number of cores matter, we set concurrent_read to 48 and 128 (depending on the CPU on the nodes) Careful with LCS it is not

Re: LCS Strategy, compaction pending tasks keep increasing

Thanks Brice for the input, I am confused as to how to calculate the value of concurrent_read, following is what i found recommended on sites and in configuration docs. concurrent_read : some places its 16 X number of drives or 4 X number of cores which of the above should i pick ? i have 40 cor

Re: LCS Strategy, compaction pending tasks keep increasing

Yes I was referring referring to multithreaded_compaction, but just because we didn’t get bitten by this setting just doesn’t mean it’s right, and the jira is a clear indication of that ;) @Anishek that reminds me of these settings to look at as well: - concurrent_write and concurrent_read bot

Re: LCS Strategy, compaction pending tasks keep increasing

I want to draw a distinction between a) multithreaded compaction (the jira I just pointed to) and b) concurrent_compactors. I'm not clear on which one you are recommending at this stage. a) Multithreaded compaction is what I warned against in my last note. b) Concurrent compactors is the number of

Re: LCS Strategy, compaction pending tasks keep increasing

Oh, thank you Sebastian for this input and the ticket reference ! We did notice an increase in CPU usage, but kept the concurrent compaction low enough for our usage, by default it takes the number of cores. We did use a number up to 30% of our available cores. But under heavy load clearly CPU is t

Re: LCS Strategy, compaction pending tasks keep increasing

Do not enable multithreaded compaction. Overhead usually outweighs any benefit. It's removed in 2.1 because it harms more than helps: https://issues.apache.org/jira/browse/CASSANDRA-6142 All the best, [image: datastax_logo.png] Sebastián Estévez Solutions Architect

Re: LCS Strategy, compaction pending tasks keep increasing

I’m not sure I get everything about storm stuff, but my understanding of LCS is that compaction count may increase the more one update data (that’s why I was wondering about duplicate primary keys). Another option is that the code is sending too much write request/s to the cassandra cluster. I don

Re: LCS Strategy, compaction pending tasks keep increasing

sorry i take that back we will modify different keys across threads not the same key, our storm topology is going to use field grouping to get updates for same keys to same set of bolts. On Tue, Apr 21, 2015 at 6:17 PM, Anishek Agarwal wrote: > @Bruice : I dont think so as i am giving each threa

Re: LCS Strategy, compaction pending tasks keep increasing

@Bruice : I dont think so as i am giving each thread a specific key range with no overlaps this does not seem to be the case now. However we will have to test where we have to modify the same key across threads -- do u think that will cause a problem ? As far as i have read LCS is recommended for s

Re: LCS Strategy, compaction pending tasks keep increasing

Could it that the app is inserting _duplicate_ keys ? -- Brice On Tue, Apr 21, 2015 at 1:52 PM, Marcus Eriksson wrote: > nope, but you can correlate I guess, tools/bin/sstablemetadata gives you > sstable level information > > and, it is also likely that since you get so many L0 sstables, you wi

Re: LCS Strategy, compaction pending tasks keep increasing

nope, but you can correlate I guess, tools/bin/sstablemetadata gives you sstable level information and, it is also likely that since you get so many L0 sstables, you will be doing size tiered compaction in L0 for a while. On Tue, Apr 21, 2015 at 1:40 PM, Anishek Agarwal wrote: > @Marcus I did l

Re: LCS Strategy, compaction pending tasks keep increasing

@Marcus I did look and that is where i got the above but it doesnt show any detail about moving from L0 -L1 any specific arguments i should try with ? On Tue, Apr 21, 2015 at 4:52 PM, Marcus Eriksson wrote: > you need to look at nodetool compactionstats - there is probably a big L0 > -> L1 compa

Re: LCS Strategy, compaction pending tasks keep increasing

I am on version 2.0.14, will update once i get the stats up for the writes again On Tue, Apr 21, 2015 at 4:46 PM, Carlos Rolo wrote: > Are you on version 2.1.x? > > Regards, > > Carlos Juzarte Rolo > Cassandra Consultant > > Pythian - Love your data > > rolo@pythian | Twitter: cjrolo | Linkedin

Re: LCS Strategy, compaction pending tasks keep increasing

Are you on version 2.1.x? Regards, Carlos Juzarte Rolo Cassandra Consultant Pythian - Love your data rolo@pythian | Twitter: cjrolo | Linkedin: *linkedin.com/in/carlosjuzarterolo * Mobile: +31 6 159 61 814 | Tel: +1 613 565 8696 x1649 www.pythian.com O

LCS Strategy, compaction pending tasks keep increasing

Hello, I am inserting about 100 million entries via datastax-java driver to a cassandra cluster of 3 nodes. Table structure is as create keyspace test with replication = {'class': 'NetworkTopologyStrategy', 'DC' : 3}; CREATE TABLE test_bits(id bigint primary key , some_bits text) with gc_grace_

Re: LCS Strategy, compaction pending tasks keep increasing

you need to look at nodetool compactionstats - there is probably a big L0 -> L1 compaction going on that blocks other compactions from starting On Tue, Apr 21, 2015 at 1:06 PM, Anishek Agarwal wrote: > the "some_bits" column has about 14-15 bytes of data per key. > > On Tue, Apr 21, 2015 at 4:34

Re: LCS Strategy, compaction pending tasks keep increasing

the "some_bits" column has about 14-15 bytes of data per key. On Tue, Apr 21, 2015 at 4:34 PM, Anishek Agarwal wrote: > Hello, > > I am inserting about 100 million entries via datastax-java driver to a > cassandra cluster of 3 nodes. > > Table structure is as > > create keyspace test with replic