If you did not use LCS until after the upgrade to 1.1.9 I think you are ok.
If in doubt the steps here look like they helped https://issues.apache.org/jira/browse/CASSANDRA-4644?focusedCommentId=13456137&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13456137 Cheers ----------------- Aaron Morton Freelance Cassandra Developer New Zealand @aaronmorton http://www.thelastpickle.com On 23/02/2013, at 6:56 AM, Mike <mthero...@yahoo.com> wrote: > Hello, > > Still doing research before we potentially move one of our column families > from Size Tiered->Leveled compaction this weekend. I was doing some research > around some of the bugs that were filed against leveled compaction in > Cassandra and I found this: > > https://issues.apache.org/jira/browse/CASSANDRA-4644 > > The bug mentions: > > "You need to run the offline scrub (bin/sstablescrub) to fix the sstable > overlapping problem from early 1.1 releases. (Running with -m to just check > for overlaps between sstables should be fine, since you already scrubbed > online which will catch out-of-order within an sstable.)" > > We recently upgraded from 1.1.2 to 1.1.9. > > Does anyone know if an offline scrub is recommended to be performed when > switching from STCS->LCS after upgrading from 1.1.2? > > Any insight would be appreciated, > Thanks, > -Mike > > On 2/17/2013 8:57 PM, Wei Zhu wrote: >> We doubled the SStable size to 10M. It still generates a lot of SSTable and >> we don't see much difference of the read latency. We are able to finish the >> compactions after repair within serveral hours. We will increase the SSTable >> size again if we feel the number of SSTable hurts the performance. >> >> ----- Original Message ----- >> From: "Mike" <mthero...@yahoo.com> >> To: user@cassandra.apache.org >> Sent: Sunday, February 17, 2013 4:50:40 AM >> Subject: Re: Size Tiered -> Leveled Compaction >> >> >> Hello Wei, >> >> First thanks for this response. >> >> Out of curiosity, what SSTable size did you choose for your usecase, and >> what made you decide on that number? >> >> Thanks, >> -Mike >> >> On 2/14/2013 3:51 PM, Wei Zhu wrote: >> >> >> >> >> I haven't tried to switch compaction strategy. We started with LCS. >> >> >> For us, after massive data imports (5000 w/seconds for 6 days), the first >> repair is painful since there is quite some data inconsistency. For 150G >> nodes, repair brought in about 30 G and created thousands of pending >> compactions. It took almost a day to clear those. Just be prepared LCS is >> really slow in 1.1.X. System performance degrades during that time since >> reads could go to more SSTable, we see 20 SSTable lookup for one read.. (We >> tried everything we can and couldn't speed it up. I think it's single >> threaded.... and it's not recommended to turn on multithread compaction. We >> even tried that, it didn't help )There is parallel LCS in 1.2 which is >> supposed to alleviate the pain. Haven't upgraded yet, hope it works:) >> >> >> http://www.datastax.com/dev/blog/performance-improvements-in-cassandra-1-2 >> >> >> >> >> >> Since our cluster is not write intensive, only 100 w/seconds. I don't see >> any pending compactions during regular operation. >> >> >> One thing worth mentioning is the size of the SSTable, default is 5M which >> is kind of small for 200G (all in one CF) data set, and we are on SSD. It >> more than 150K files in one directory. (200G/5M = 40K SSTable and each >> SSTable creates 4 files on disk) You might want to watch that and decide the >> SSTable size. >> >> >> By the way, there is no concept of Major compaction for LCS. Just for fun, >> you can look at a file called $CFName.json in your data directory and it >> tells you the SSTable distribution among different levels. >> >> >> -Wei >> >> >> >> >> >> From: Charles Brophy <cbro...@zulily.com> >> To: user@cassandra.apache.org >> Sent: Thursday, February 14, 2013 8:29 AM >> Subject: Re: Size Tiered -> Leveled Compaction >> >> >> I second these questions: we've been looking into changing some of our CFs >> to use leveled compaction as well. If anybody here has the wisdom to answer >> them it would be of wonderful help. >> >> >> Thanks >> Charles >> >> >> On Wed, Feb 13, 2013 at 7:50 AM, Mike < mthero...@yahoo.com > wrote: >> >> >> Hello, >> >> I'm investigating the transition of some of our column families from Size >> Tiered -> Leveled Compaction. I believe we have some high-read-load column >> families that would benefit tremendously. >> >> I've stood up a test DB Node to investigate the transition. I successfully >> alter the column family, and I immediately noticed a large number (1000+) >> pending compaction tasks become available, but no compaction get executed. >> >> I tried running "nodetool sstableupgrade" on the column family, and the >> compaction tasks don't move. >> >> I also notice no changes to the size and distribution of the existing >> SSTables. >> >> I then run a major compaction on the column family. All pending compaction >> tasks get run, and the SSTables have a distribution that I would expect from >> LeveledCompaction (lots and lots of 10MB files). >> >> Couple of questions: >> >> 1) Is a major compaction required to transition from size-tiered to leveled >> compaction? >> 2) Are major compactions as much of a concern for LeveledCompaction as their >> are for Size Tiered? >> >> All the documentation I found concerning transitioning from Size Tiered to >> Level compaction discuss the alter table cql command, but I haven't found >> too much on what else needs to be done after the schema change. >> >> I did these tests with Cassandra 1.1.9. >> >> Thanks, >> -Mike >> >> >> >> >> >
