Re: CreateFile() and FILE_FLAG_WRITE_THROUGH

See the white paper I posted at my web site www.msftmvp.com "Application data/meta data caching best practices"

Its not a simple explanation, but hopefully you will find the paper answers your questions

"Nick Tucker" <nick.tucker@xxxxxxxxxxxxxxxxx> wrote in message news:FCE45230-0DDB-47EC-9B11-CD5B09758B46@xxxxxxxxxxxxxxxx
Hi everyone

If I create a file using CreateFile(), specifying the
FILE_FLAG_WRITE_THROUGH flag, then write to that file, the file still shows
as zero bytes long in the directory and in Windows Explorer, and if I then
turn the power off, that file is still zero bytes long on restart, so the
data I wrote is unavailable. I have tried this test on a variety of
operating systems including Vista, XP and Windows Server 2003/2008 using a
variety of hardware platforms with both SATA and SCSI disk systems, and they
all behave the same way.

Surely the whole point of specifying that flag is that I want the data to be
written to disk, together with it's corresponding metadata, so if a
catastrophic failure occurs, the data is available to me on restart.

My researches of newsgroup articles on this subject suggest that if I want
this, then I also have to use FlushFileBuffers(), but if that is so then
surely I don't need to specify the write through flag since all file and
folder data will be committed to disk when I call that function.

So, what is the point of specifying the write-through flag in this scenario?

I think the documentation of CreateFile() could do with a little
clarification!

Thanks in advance for responses.

Nick


.

Relevant Pages

  • Re: CreateFile() and FILE_FLAG_WRITE_THROUGH
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