Since you moved from size tiered compaction. All your sstables are in L0. You might be hitting this. Copied from code. // LevelDB gives each level a score of how much data it contains vs its ideal amount, and // compacts the level with the highest score. But this falls apart spectacularly once you // get behind. Consider this set of levels: // L0: 988 [ideal: 4] // L1: 117 [ideal: 10] // L2: 12 [ideal: 100] // // The problem is that L0 has a much higher score (almost 250) than L1 (11), so what we'll // do is compact a batch of MAX_COMPACTING_L0 sstables with all 117 L1 sstables, and put the // result (say, 120 sstables) in L1. Then we'll compact the next batch of MAX_COMPACTING_L0, // and so forth. So we spend most of our i/o rewriting the L1 data with each batch. // // If we could just do *all* L0 a single time with L1, that would be ideal. But we can't // -- see the javadoc for MAX_COMPACTING_L0. // // LevelDB's way around this is to simply block writes if L0 compaction falls behind. // We don't have that luxury. // // So instead, we // 1) force compacting higher levels first, which minimizes the i/o needed to compact // optimially which gives us a long term win, and // 2) if L0 falls behind, we will size-tiered compact it to reduce read overhead until // we can catch up on the higher levels. // // This isn't a magic wand -- if you are consistently writing too fast for LCS to keep // up, you're still screwed. But if instead you have intermittent bursts of activity, // it can help a lot.
On Tue, Jul 9, 2013 at 3:23 PM, PARASHAR, BHASKARJYA JAY <bp1...@att.com>wrote: > Thanks Sankalp…I will look at these.**** > > ** ** > > *From:* sankalp kohli [mailto:kohlisank...@gmail.com] > *Sent:* Tuesday, July 09, 2013 3:22 PM > *To:* user@cassandra.apache.org > > *Subject:* Re: Leveled Compaction, number of SStables growing.**** > > ** ** > > Do you have lot of sstables in L0? **** > > Since you moved from size tiered compaction with lot of data, it will take > time for it to compact. **** > > You might want to increase the compaction settings to speed it up. **** > > ** ** > > On Tue, Jul 9, 2013 at 12:33 PM, PARASHAR, BHASKARJYA JAY <bp1...@att.com> > wrote:**** > > Thanks Jake. Guess we will have to increase the size.**** > > **** > > *From:* Jake Luciani [mailto:jak...@gmail.com] > *Sent:* Tuesday, July 09, 2013 2:05 PM > *To:* user > *Subject:* Re: Leveled Compaction, number of SStables growing.**** > > **** > > We run with 128mb some run with 256mb. Leveled compaction creates fixed > sized sstables by design so this is the only way to lower the file count.* > *** > > **** > > On Tue, Jul 9, 2013 at 2:56 PM, PARASHAR, BHASKARJYA JAY <bp1...@att.com> > wrote:**** > > Hi,**** > > **** > > We recently switched from size tired compaction to Leveled compaction. We > made this change because our rows are frequently updated. We also have a > lot of data.**** > > With size-tiered compaction, we have about 5-10 sstables per CF. So with > about 15 CF’s we had about 100 sstables.**** > > With a sstable default sixe of 5mb, now after leveled compaction, we have > about 130k sstables and growing as the writes increases. There are a lot of > compaction jobs pending.**** > > If we increase the SStable size to 20mb, that will be about 30k sstables > but it’s still a lot.**** > > **** > > Is this common? Any solution, hints on reducing the sstables are welcome.* > *** > > **** > > Thanks**** > > -Jay**** > > > > **** > > **** > > -- > http://twitter.com/tjake ** ** > > ** ** >