Nikolai, Are you sure about 1.26Gb? Like it doesn't look right - 5195 tables with 256Mb table size...
Andrei On Mon, Nov 24, 2014 at 5:09 PM, Nikolai Grigoriev <ngrigor...@gmail.com> wrote: > Jean-Armel, > > I have only two large tables, the rest is super-small. In the test cluster > of 15 nodes the largest table has about 110M rows. Its total size is about > 1,26Gb per node (total disk space used per node for that CF). It's got about > 5K sstables per node - the sstable size is 256Mb. cfstats on a "healthy" > node look like this: > > Read Count: 8973748 > Read Latency: 16.130059053251774 ms. > Write Count: 32099455 > Write Latency: 1.6124713938912671 ms. > Pending Tasks: 0 > Table: wm_contacts > SSTable count: 5195 > SSTables in each level: [27/4, 11/10, 104/100, 1053/1000, 4000, 0, > 0, 0, 0] > Space used (live), bytes: 1266060391852 > Space used (total), bytes: 1266144170869 > SSTable Compression Ratio: 0.32604853410787327 > Number of keys (estimate): 25696000 > Memtable cell count: 71402 > Memtable data size, bytes: 26938402 > Memtable switch count: 9489 > Local read count: 8973748 > Local read latency: 17.696 ms > Local write count: 32099471 > Local write latency: 1.732 ms > Pending tasks: 0 > Bloom filter false positives: 32248 > Bloom filter false ratio: 0.50685 > Bloom filter space used, bytes: 20744432 > Compacted partition minimum bytes: 104 > Compacted partition maximum bytes: 3379391 > Compacted partition mean bytes: 172660 > Average live cells per slice (last five minutes): 495.0 > Average tombstones per slice (last five minutes): 0.0 > > Another table of similar structure (same number of rows) is about 4x times > smaller. That table does not suffer from those issues - it compacts well and > efficiently. > > On Mon, Nov 24, 2014 at 2:30 AM, Jean-Armel Luce <jaluc...@gmail.com> wrote: >> >> Hi Nikolai, >> >> Please could you clarify a little bit what you call "a large amount of >> data" ? >> >> How many tables ? >> How many rows in your largest table ? >> How many GB in your largest table ? >> How many GB per node ? >> >> Thanks. >> >> >> >> 2014-11-24 8:27 GMT+01:00 Jean-Armel Luce <jaluc...@gmail.com>: >>> >>> Hi Nikolai, >>> >>> Thanks for those informations. >>> >>> Please could you clarify a little bit what you call " >>> >>> 2014-11-24 4:37 GMT+01:00 Nikolai Grigoriev <ngrigor...@gmail.com>: >>>> >>>> Just to clarify - when I was talking about the large amount of data I >>>> really meant large amount of data per node in a single CF (table). LCS does >>>> not seem to like it when it gets thousands of sstables (makes 4-5 levels). >>>> >>>> When bootstraping a new node you'd better enable that option from >>>> CASSANDRA-6621 (the one that disables STCS in L0). But it will still be a >>>> mess - I have a node that I have bootstrapped ~2 weeks ago. Initially it >>>> had >>>> 7,5K pending compactions, now it has almost stabilized ad 4,6K. Does not go >>>> down. Number of sstables at L0 is over 11K and it is slowly slowly >>>> building >>>> upper levels. Total number of sstables is 4x the normal amount. Now I am >>>> not >>>> entirely sure if this node will ever get back to normal life. And believe >>>> me >>>> - this is not because of I/O, I have SSDs everywhere and 16 physical cores. >>>> This machine is barely using 1-3 cores at most of the time. The problem is >>>> that allowing STCS fallback is not a good option either - it will quickly >>>> result in a few 200Gb+ sstables in my configuration and then these sstables >>>> will never be compacted. Plus, it will require close to 2x disk space on >>>> EVERY disk in my JBOD configuration...this will kill the node sooner or >>>> later. This is all because all sstables after bootstrap end at L0 and then >>>> the process slowly slowly moves them to other levels. If you have write >>>> traffic to that CF then the number of sstables and L0 will grow quickly - >>>> like it happens in my case now. >>>> >>>> Once something like https://issues.apache.org/jira/browse/CASSANDRA-8301 >>>> is implemented it may be better. >>>> >>>> >>>> On Sun, Nov 23, 2014 at 4:53 AM, Andrei Ivanov <aiva...@iponweb.net> >>>> wrote: >>>>> >>>>> Stephane, >>>>> >>>>> We are having a somewhat similar C* load profile. Hence some comments >>>>> in addition Nikolai's answer. >>>>> 1. Fallback to STCS - you can disable it actually >>>>> 2. Based on our experience, if you have a lot of data per node, LCS >>>>> may work just fine. That is, till the moment you decide to join >>>>> another node - chances are that the newly added node will not be able >>>>> to compact what it gets from old nodes. In your case, if you switch >>>>> strategy the same thing may happen. This is all due to limitations >>>>> mentioned by Nikolai. >>>>> >>>>> Andrei, >>>>> >>>>> >>>>> On Sun, Nov 23, 2014 at 8:51 AM, Servando Muñoz G. <smg...@gmail.com> >>>>> wrote: >>>>> > ABUSE >>>>> > >>>>> > >>>>> > >>>>> > YA NO QUIERO MAS MAILS SOY DE MEXICO >>>>> > >>>>> > >>>>> > >>>>> > De: Nikolai Grigoriev [mailto:ngrigor...@gmail.com] >>>>> > Enviado el: sábado, 22 de noviembre de 2014 07:13 p. m. >>>>> > Para: user@cassandra.apache.org >>>>> > Asunto: Re: Compaction Strategy guidance >>>>> > Importancia: Alta >>>>> > >>>>> > >>>>> > >>>>> > Stephane, >>>>> > >>>>> > As everything good, LCS comes at certain price. >>>>> > >>>>> > LCS will put most load on you I/O system (if you use spindles - you >>>>> > may need >>>>> > to be careful about that) and on CPU. Also LCS (by default) may fall >>>>> > back to >>>>> > STCS if it is falling behind (which is very possible with heavy >>>>> > writing >>>>> > activity) and this will result in higher disk space usage. Also LCS >>>>> > has >>>>> > certain limitation I have discovered lately. Sometimes LCS may not be >>>>> > able >>>>> > to use all your node's resources (algorithm limitations) and this >>>>> > reduces >>>>> > the overall compaction throughput. This may happen if you have a >>>>> > large >>>>> > column family with lots of data per node. STCS won't have this >>>>> > limitation. >>>>> > >>>>> > >>>>> > >>>>> > By the way, the primary goal of LCS is to reduce the number of >>>>> > sstables C* >>>>> > has to look at to find your data. With LCS properly functioning this >>>>> > number >>>>> > will be most likely between something like 1 and 3 for most of the >>>>> > reads. >>>>> > But if you do few reads and not concerned about the latency today, >>>>> > most >>>>> > likely LCS may only save you some disk space. >>>>> > >>>>> > >>>>> > >>>>> > On Sat, Nov 22, 2014 at 6:25 PM, Stephane Legay >>>>> > <sle...@looplogic.com> >>>>> > wrote: >>>>> > >>>>> > Hi there, >>>>> > >>>>> > >>>>> > >>>>> > use case: >>>>> > >>>>> > >>>>> > >>>>> > - Heavy write app, few reads. >>>>> > >>>>> > - Lots of updates of rows / columns. >>>>> > >>>>> > - Current performance is fine, for both writes and reads.. >>>>> > >>>>> > - Currently using SizedCompactionStrategy >>>>> > >>>>> > >>>>> > >>>>> > We're trying to limit the amount of storage used during compaction. >>>>> > Should >>>>> > we switch to LeveledCompactionStrategy? >>>>> > >>>>> > >>>>> > >>>>> > Thanks >>>>> > >>>>> > >>>>> > >>>>> > >>>>> > -- >>>>> > >>>>> > Nikolai Grigoriev >>>>> >>>> >>>> >>>> >>>> -- >>>> Nikolai Grigoriev >>>> >>> >> > > > > -- > Nikolai Grigoriev >
