De acordo com este snippet deste artigo do TechNet , parece que o administrador da pesquisa DB é alocado 10GB de espaço na criação.
Search requires three databases. Your environment may include multiple Property and Crawl databases.
The Search administration database is typically small: allocate 10 GB.
To estimate the required storage for your Property and Crawl databases, use the following multipliers: Crawl: 0.046 × (sum of content databases) Property: 0.015 × (sum of content databases)
The IOPS requirements for Search are significant. For the Crawl database, search requires from 3,500 to 7,000 IOPS.
For the Property database, search requires 2,000 IOPS.
For detailed information about how to estimate capacity required for Search, see Performance and capacity test results and recommendations (SharePoint Server 2010).