C＃：FileStream.SetLength（long）失败，并显示“由于文件系统限制，请求的操作无法完成”（在Windows 10 Home，NTFS上）

Question

I had a very confusing experience with the System.IO.FileStream when writing a fairly large file that was approaching 8Gb in size***. The call to FileStream.SetLength(LARGE_NUMBER) started to suddenly fail with the error

The requested operation could not be completed due to a file system limitation

The stacktrace was:

   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileStream.SetLengthCore(Int64 value)
   at System.IO.FileStream.SetLength(Int64 value)
   at LiteDB.FileDiskService.WriteJournal(ICollection`1 pages, UInt32 lastPageID)
   ...

This was reproducible and fairly puzzling as googling turned up no obvious answer.

For the record, the LARGE_NUMBER SetLength was being called with was around 8,110,000,000 -- not small, but not in any way special. I've certainly seen larger files on NTFS before.

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*** It's a LiteDB database file -- I do recognise I'm probably stretching what it is meant to be used for but this isn't the point of the question.

Answer 1

While I cannot say I have found the exact explanation of what the problem was, I managed to resolve the problem and enable my program to continue extending this file.

I cannot say if this was related, but I noticed a line at https://support.microsoft.com/en-us/help/967351/a-heavily-fragmented-file-in-an-ntfs-volume-may-not-grow-beyond-a-cert saying the following:

A heavily fragmented file in an NTFS file system volume may not grow beyond a certain size caused by an implementation limit in structures that are used to describe the allocations.

Since I had no other ideas left, I thought I'd try simply making a copy of the file and hoping that the copy would end up less fragmented than a file that was written very gradually in small increments over a long time. Amazingly, this worked, and FileStream.SetLength(LARGE_NUMBER) on the copy of the old file started working again.

Interestingly, before I made a copy, I tried renaming the old problematic file and I could not do even that, getting a Windows error popup saying the same thing about the file system limitation.