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From Shawn Heisey <apa...@elyograg.org>
Subject Re: Solr 7.2.1 Collection Backup Performance issue
Date Tue, 18 Sep 2018 19:42:51 GMT
On 9/18/2018 11:00 AM, Ganesh Sethuraman wrote:
> We are using Solr 7.2.1 with SolrCloud with 35 collections with 1 node ZK
> ensemble (in lower environment, we will have 3 nodes ensemble) in AWS. We
> are testing to see if we have Async Solr Cloud backup  (
> https://lucene.apache.org/solr/guide/7_2/collections-api.html#backup) done
> every time we are create a new collection or update an existing collection.
> There are 1 replica and 8 shards per collection. Two Solr nodes.
>
> For the largest collection (index size of 80GB), we see that BACKUP to the
> EFS drive takes about ~10 mins. We are doing lot of /get (real time get)
> option from the application. We are seeing that that the performance
> significantly (2x) degrades on the read (get) performance when we BACK-UP
> is going on in parallel.

My best guess here is that you do not have enough memory. For good 
performance, Solr is extremely reliant on having certain parts of the 
index data sitting in memory, so that it doesn't have to actually read 
the disk to discover matches for a query.  When all is working well, 
that data will be read from memory instead of the disk.  Memory is MUCH 
MUCH faster than a disk.

Making a backup is going to read ALL of the index data.  So if you do 
not have enough spare memory to cache the entire index, reading the 
index to make the backup is going to push the important parts of the 
index out of the cache, and then Solr will have to actually go and read 
the disk in order to satisfy a query.

https://wiki.apache.org/solr/SolrPerformanceProblems#RAM

Can you gather a screenshot of your process list and put it on a file 
sharing website?  You'll find instructions on how to do this here:

https://wiki.apache.org/solr/SolrPerformanceProblems#Asking_for_help_on_a_memory.2Fperformance_issue

Thanks,
Shawn


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