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
>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 >, 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
>>-----Original-Nachricht-----
>>Von: Maximiliano Gazquez < maximiliano....@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 >
>>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!
