Just to be explicit: you’ll need nearly twice as much memory if you increase the number of backups from 2 to 4. With the same size cluster, chances are a lot of the data is going to be on-disk rather than in-memory.
It’s very unusual to need five copies of the data. Backups=1 is sufficient for most use cases. > On 1 Dec 2021, at 06:15, Zhenya Stanilovsky <arzamas...@mail.ru> wrote: > > hello Maximiliano Gazquez, good question ! But there is no one strength > answer on it. > > > I assumed that queries are distributed and each node answers the query only > > with its primary partitions and adding backups wouldn’t affect performance. > Ok, but what about overall system performance degradation ? Check page > replacement [1] algo, more efficient was introduced in new versions, thus > upgrade to new ver is welcomes. Second — wal it`s all about io usage. Do you > have monitoring of your disk io activity ? 4 Backups means 5 nodes with equal > data, is it really necessary or you just make a research ? Also additional > work for index rebuilding i hope. > > [1] > https://cwiki.apache.org/confluence/display/IGNITE/IEP-62+Page+replacement+improvements > > <https://cwiki.apache.org/confluence/display/IGNITE/IEP-62+Page+replacement+improvements> > > > My problem is 100% with queries, not writes. > It’s the same cluster, same hardware, but a LOT slower when using 4 backups > instead of 2. > > Is there any metric that I could check to find out what’s happening? > > Thanks! > On 30 Nov 2021 15:42 -0300, Henrik <ho...@magenta.de > <x-msg://24/compose?To=ho...@magenta.de>>, wrote: >> With more backups the cluster has the worse writing performance since data >> will be copied by multiple times. But the reading performance should be >> increased since each node answers the request from local backup. >> >> Thanks >> >> >> Gesendet mit der Telekom Mail App >> <http://www.t-online.de/service/redir/emailmobilapp_ios_smartphone_footerlink.htm> >> -----Original-Nachricht----- >> Von: Maximiliano Gazquez <maximiliano....@gmail.com >> <x-msg://e.mail.ru/compose/?mailto=mailto%3amaximiliano....@gmail.com>> >> Betreff: [2.8.1] Having more backups make SQL queries slower. >> Datum: 01.12.2021, 00:12 Uhr >> An: <user@ignite.apache.org >> <x-msg://e.mail.ru/compose/?mailto=mailto%3au...@ignite.apache.org>> >> >> Hello everyone. >> >> We are doing some testing in a 10 node cluster which we use as a distributed >> database with persistence enabled. >> Each node has 6gb region size + 5gb heap. >> All caches are partitioned, and I connect to the cluster using the thin >> client. >> >> I’ve found a performance issue: >> With 2 backups, the performance is pretty great. >> With 4 backups the performance is really bad. >> So I wanted to ask why would this happen. >> >> I assumed that queries are distributed and each node answers the query only >> with its primary partitions and adding backups wouldn’t affect performance. >> >> Thanks everyone! > > > >
