Im getting a lot of these error since 2 days back:

2015-10-28 00:00:02,098       ERROR        ?.? - Failed to delete Document with id: 636e8ad8-b7d8-4222-8860-9d973a694ead|iv. Message: did not read all bytes from file "_il34e.fnm": read 1 vs size 553
   at Lucene.Net.Index.SegmentInfos.FindSegmentsFile.Run(IndexCommit commit) in d:\Lucene.Net\FullRepo\trunk\src\core\Index\SegmentInfos.cs:line 585
   at Lucene.Net.Index.DirectoryReader.Open(Directory directory, IndexDeletionPolicy deletionPolicy, IndexCommit commit, Boolean readOnly, Int32 termInfosIndexDivisor) in d:\Lucene.Net\FullRepo\trunk\src\core\Index\DirectoryReader.cs:line 117
   at EPiServer.Search.IndexingService.IndexingServiceHandler.DeleteFromIndex(NamedIndex namedIndex, String itemId, Boolean deleteRef)
2015-10-28 00:00:02,098       ERROR        ?.? - An exception was thrown when task was invoked by TaskQueue: 'indexing service data uri callback'. The message was: Object reference not set to an instance of an object.. Stacktrace was:    at EPiServer.Search.IndexingService.IndexingServiceSettings.SetResponseHeaderStatusCode(Int32 statusCode)
   at EPiServer.Search.IndexingService.IndexingServiceHandler.DeleteFromIndex(NamedIndex namedIndex, String itemId, Boolean deleteRef)
   at EPiServer.Search.IndexingService.IndexingServiceHandler.Remove(String itemId, NamedIndex namedIndex, Boolean removeRef)
   at EPiServer.Search.IndexingService.IndexingServiceHandler.Update(SyndicationItem item, NamedIndex namedIndex)
   at EPiServer.Search.IndexingService.IndexingServiceHandler.HandleDataUri(SyndicationItem item, NamedIndex namedIndex)
   at EPiServer.Search.IndexingService.TaskQueue.Timer_Elapsed(Object sender, ElapsedEventArgs e)

CMS 8.10

There is 441592 rows in tblIndexRequestLog    

My config is:

The files under datapath\index are two days old.

Any idea?