HI

we have search service application scaled to

-2 index servers 2 wfe servers running query components

here  i created content sources for web applications.

-in sql server there is search_crawl database is very huge ( 500 GB) , i dont know how its happen

-we scheduled incremental crawling for time span 5 minus for content sources

Here you go. This should help you

http://community.aiim.org/blogs/michael-doyle/2010/12/17/is-your-search-database-bloated

http://blog.sisq.info/en/2013/04/sharepoint-2010-search-db-crawl-store-is-to-large/

Hi,

According to your post, my understanding is that you want to know why search_crawl database become huge size in sql server.

Crawl logs are maintained for a very long time by default (it appears to be 30 days), there isnt a way to configure this in the GUI.  Only errors are logged, and theyre logged with the frequency of the indexing crawl schedule. 

This database will grow huge if you are crawling a lot of data (such as a file share) and it doesnt do a great job of cleaning up after itself.

To reduce the database, you can refer to:

SharePoint 2010: Manage the Crawl Database Size

Sharepoint 2010: Search DB Crawl Store is to large

SharePoint 2010 Application Crawl Store DB Grows Out of Control

Best Regards,

Linda Li