Search: Primary and Replica Index not the same size?

Question

I have a question regarding size of index partition. My Search Application Topology looks like that:

Checking the status of my SSA shows everything in Active State, nothing degraded.

But the Size of the index is different. Does anybody know, why? Here's a screenshot of Primary and Replica Index Content/Size of both WFE Servers. Each Folder "SPSearchService" contain the subfolders "PrimaryIndex" and "ReplicaIndex".

I thought the index on both servers have to be the same size?

Edit: I generated a report for a full overview:

Answer 1

I do not know what caused this issue (once I was out of disk space, maybe this caused the fail in merging the index), but I could fix it.

First I did an Index Reset (in Search Administration) and checked, if the index files on my servers are deleted. Then I started full crawling on every content source I have.

Now the ratio of my index components looks much healthier:

-----------------------------------------
[ SharePoint Search Service Application ]
-----------------------------------------

Host     State  Name            CellName Partition Primary Generation ActiveDocs Merging CheckpointSize
----     -----  ----            -------- --------- ------- ---------- ---------- ------- --------------
xxxxx059 Active IndexComponent5 [I.0.0]          0    True       5264    1516121   False 34423 (MB)    
xxxxx154 Active IndexComponent7 [I.1.0]          0   False       5264    1516121   False 34458.7 (MB)  
xxxxx059 Active IndexComponent6 [I.0.1]          1    True       5264    1515190   False 34297.3 (MB)  
xxxxx154 Active IndexComponent8 [I.1.1]          1   False       5264    1515190   False 34297.5 (MB)  



ServerName Name            Drive Capacity Available Space Size on Disk Path                                            
---------- ----            -------------- --------------- ------------ ----                                            
xxxxx059   IndexComponent5 153469 MB      80739.6 MB      35056.8 MB   D:\SPSearchService\PrimaryIndex\SPf90231c0687...
xxxxx059   IndexComponent6 153469 MB      80739.7 MB      35154.4 MB   D:\SPSearchService\ReplicaIndex\SPf90231c0687...
xxxxx154   IndexComponent7 153469 MB      80255.5 MB      35145.9 MB   D:\SPSearchService\ReplicaIndex\SPf90231c0687...
xxxxx154   IndexComponent8 153469 MB      80255.5 MB      35154.8 MB   D:\SPSearchService\PrimaryIndex\SPf90231c0687...



Component       UpdateGroup TargetRatio   Total  Master Time                Ratio
---------       ----------- -----------   -----  ------ ----                -----
IndexComponent5 %default    10%         1521141 1502373 05.11.2015 09:03:03 1.23%
IndexComponent5 link        10%         1515464 1401709 05.11.2015 09:03:03 7.51%
IndexComponent5 people      10%             661     661 05.11.2015 09:03:03 0.00%
IndexComponent5 security    10%         1521365 1400995 05.11.2015 09:03:03 7.91%
IndexComponent5 usage       10%            6202    6202 05.11.2015 09:03:03 0.00%
IndexComponent6 %default    10%         1520228 1481600 05.11.2015 09:03:03 2.54%
IndexComponent6 link        10%         1514542 1400506 05.11.2015 09:03:03 7.53%
IndexComponent6 people      10%             652     652 05.11.2015 09:03:03 0.00%
IndexComponent6 security    10%         1520465 1399616 05.11.2015 09:03:03 7.95%
IndexComponent6 usage       10%            6215    6215 05.11.2015 09:03:03 0.00%
IndexComponent7 %default    10%         1521140 1510511 05.11.2015 09:03:03 0.70%
IndexComponent7 link        10%         1515464 1401709 05.11.2015 09:03:03 7.51%
IndexComponent7 people      10%             661     661 05.11.2015 09:03:03 0.00%
IndexComponent7 security    10%         1521361 1415827 05.11.2015 09:03:03 6.94%
IndexComponent7 usage       10%            6202    6202 05.11.2015 09:03:03 0.00%
IndexComponent8 %default    10%         1520228 1481600 05.11.2015 09:03:03 2.54%
IndexComponent8 link        10%         1514542 1400506 05.11.2015 09:03:03 7.53%
IndexComponent8 people      10%             652     652 05.11.2015 09:03:03 0.00%
IndexComponent8 security    10%         1520456 1413821 05.11.2015 09:03:03 7.01%
IndexComponent8 usage       10%            6215    6215 05.11.2015 09:03:03 0.00%


Health Reports for Index System SPf90231c06878 of Constellation 3CCEF9:

Name                                Message        Level
----                                -------        -----
active_indexrouters[SPf90231c06878] [I.0.0, I.0.1] Info 
in_sync[SPf90231c06878.0]           [I.0.0, I.1.0] Info 
in_sync[SPf90231c06878.1]           [I.0.1, I.1.1] Info 
left_behind[SPf90231c06878.0]       []             Info 
left_behind[SPf90231c06878.1]       []             Info 
members[SPf90231c06878.0]           [I.1.0, I.0.0] Info 
members[SPf90231c06878.1]           [I.1.1, I.0.1] Info 
primary[SPf90231c06878.0]           I.0.0          Info 
primary[SPf90231c06878.1]           I.0.1          Info 



Primary Search Admin for Constellation 3CCEF9: NodeRunnerAdmin1 on prds0058

Home directory for SharePoint Search Service Application's Constellation:
C:\Program Files\Microsoft Office Servers\15.0\Data\Office Server\Applications\Search\Nodes\3CCEF9

So, something messed up my index and I could repair it by resetting the index.