I've expanded the disks where the search index is...manually monitoring the Disk usage...and I've

used the formel (ContentSize x 0.35)  it shouldn't extend to more than 500 GB - during the weekend it has now exceed this limit...

Whats going on? - Friday the free disk space was +190GB - and Monday only 70GB free ! 

Why all of the sudden it takes all this disk space? - (No content is added during the weekend that can explain this)  

would like to prevent that the disk runs out of space...

Is there a resource where I can "read" more about index components (FAST) "strange" behavior? - what to expect and what not to expect?

Furthermore - All the Health reports - is all blank.... 

If I run extended search topology (script from the searchengineers) 

SSA: Search Service Application

Component                     Server   Partition State 
---------                     ------   --------- ----- 
AdminComponent1               APP1           Active
AnalyticsProcessingComponent1 APP1           Active
AnalyticsProcessingComponent2 WFE1           Active
ContentProcessingComponent1   APP1           Active
ContentProcessingComponent2   WFE1           Active
CrawlComponent0               APP1           Active
CrawlComponent1               WFE1           Active
IndexComponent10 (Primary)    APP1 0         Active
IndexComponent11              WFE1 0         Active
QueryProcessingComponent1     APP1           Active
QueryProcessingComponent2     WFE1           Active



Primary search host controller (for dictionary repository): APP1

Analytics Processing Job Status:
    SearchAnalytics : Idle
        Last successful start time: 22-06-2015 00:00:03
        Last completed time: 22-06-2015 01:40:36
        Next scheduled run time: 23-06-2015 00:00:00
    UsageAnalytics : Idle
        Last successful start time: 22-06-2015 01:00:02
        Last completed time: 22-06-2015 01:28:32
    SearchReports : Idle
        Last successful start time: 22-06-2015 04:10:00
        Last completed time: 22-06-2015 04:10:30
        Next scheduled run time: 23-06-2015 02:01:00

Searchable items: 3808681
Crawling CS1 : CrawlingIncremental
Crawling CS2 : CrawlingIncremental
Crawling CS3 : CrawlingIncremental
Crawling CS4 : CrawlingIncremental
Crawling CS5 : CrawlingIncremental
Search service overall state: OK

can someone please advise?