File size on disk bigger than expected with file stream

Hello,

we use a NAS to archive stream from database to files. If we look at the file size on disk, it is bigger than expected.

For example : 

File size is 127K

ls -alh | grep write-chupmb-pdf
127K 2020-07-02 10:43 write-chupmb-pdf

Size on disk  is 192K

du -sh * | grep write-chupmb-pdf
192K    write-chupmb-pdf

Or expected size is 128K (with 4K blocs)

I tried with %Stream.FileBinary, %FileBinaryStream and OPEN/USE/WRITE and with multiple files and file type (PDF, JPG, PNG) and I have the same problem each time.

For example :

du -sh * | grep write-chupmb-pdf
192K    write-chupmb-pdf
192K    write-chupmb-pdf-copyfrom
224K    write-chupmb-pdf-raw
192K    write-chupmb-pdf-tmpstream

And the code to generate these files

//stream variable come from database (%GlobalBinaryStream)

//write-chupmb-pdf-copyfrom
SET fileNAS = ##class(%Stream.FileBinary).%New()
DO fileNAS.FilenameSet("\\nas-chup-7d\TSarchives\2018\TEST\write-chupmb-pdf-copyfrom")
WRITE fileNAS.CopyFromAndSave(stream),!
DO stream.Rewind() 

//write-chupmb-pdf
SET fileNAS = ##class(%Stream.FileBinary).%New()
DO fileNAS.FilenameSet("\\nas-chup-7d\TSarchives\2018\TEST\write-chupmb-pdf")
WHILE 'stream.AtEnd {
DO fileNAS.Write(stream.Read()) 
}
WRITE fileNAS.%Save(),!
DO stream.Rewind() 

//write-chupmb-pdf-tmpstream
SET tmpStream = ##class(%Stream.GlobalBinary).%New()
DO tmpStream.CopyFrom(stream) 
SET fileNAS = ##class(%Stream.FileBinary).%New()
DO fileNAS.FilenameSet("\\nas-chup-7d\TSarchives\2018\TEST\write-chupmb-pdf-tmpstream")
WRITE fileNAS.CopyFromAndSave(stream),!
DO stream.Rewind()  

// write-chupmb-pdf-raw
SET fileNASRAW = "\\nas-chup-7d\TSarchives\2018\TEST\write-chupmb-pdf-raw"
OPEN fileNASRAW:("WSN")
USE fileNASRAW
WHILE 'stream.AtEnd {
WRITE stream.Read() 
}
CLOSE fileNASRAW

I also compared with streams written by other technologies than Caché and we have no problem with them.

Has anyone ever encountered this kind of problem ?

Caché version is : Cache for Windows (x86-64) 2017.2.2 (Build 865U) Mon Jun 25 2018 10:33:28 EDT

Thank you

Yann