Does solr by default creates or .cfs segment file or is it based on the config?

Question

Am having doubt i have solr 5.2.1 running on linux machine, when i check the segment files in the index data directory i see lot of .cfs file(which is compound file segment) more details here in https://lucene.apache.org/solr/guide/6_6/indexconfig-in-solrconfig.html#IndexConfiginSolrConfig-CompoundFileSegments .

Is it good to have .cfs file for performance and replication activity. Because i see lot of full copy replication happening on the salve side.

I did a comparison with another solr environment where i run 4.2.1 on windows machine. I don't see any segment file in index data directory with *.cfs and the only difference between these two environment in config is i see that

<usecompoundfile>false</usecompoundfile>  

The above config is explicitly defined in the solr which am running on windows, but in the solr which i run on linux i haven't defined any such since by default it will be treated as false. Could anyone please clarify me on this.

Thanks

Answer 1

You can check the docs for your relevant version. In 6.6 the default is false, and probably for you too.

The performance may be slightly lower with Compound File Segments , but can help reduce the number of open files:

CFS segments may incur a minor performance hit for various reasons, depending on the runtime environment. For example, filesystem buffers are typically associated with open file descriptors, which may limit the total cache space available to each index.

On systems where the number of open files allowed per process is limited, CFS may avoid hitting that limit. The open files limit might also be tunable for your OS with the Linux/Unix ulimit command, or something similar for other operating systems.