I am writing a little application, which is writing jpeg images at a constant rate on a SD card. I choose an EXT3 filesystem, but the same behaviour was observed with an EXT2 filesystem. My writing loop looks like this : get_image() fwrite() fsync() Or like this : get_image() fopen() fwrite() fsync() fclose() I also display some ...
I want to make sure that an ofstream has been written to the disk device. What's the portable way (portable on POSIX systems) of doing this? Does that solve the problem if I open the file separately in read-only append mode to get a file descriptor and call fsync with it? Like this: ofstream out(filename); /* ... write content into ...
Hi I am trying to do a wear leveling test on a series of SD cards. I relation to this my idea was to use dd to write, read, rewrite and reread the same "first block" on the SD card - my for doing this is the following - dd if=data of=/dev/sdb bs=512 count=1 conv=fsync rm readdata >/dev/null dd if=/dev/sdb of=readdata bs=512 count=1 con...
Hi Will the conv=fsync flag when using dd, flush the data directly? /Jesper ...
I thought fsync() does fflush() internally so using fsync() on a stream is OK. But i am getting unexpected result when executed under network I/O. My code snippet: FILE* fp = fopen(file,"wb"); /* multiple fputs() call like: */ fputs(buf, fp); ... ... fputs(buf.c_str(), fp); /* get fd of the FIL...
In my program, I hold two files open for writing, a content-file, containing chunks of data, and an index-file, containing a map over which chunks of data has been written so far. I would like to flush them both to disc, as performant as possible, with the only constraint that the blocks in the data-file must be written before the corre...
What's the correct way to durably rename a file in a POSIX file system? Specifically wondering about fsyncs on the directories. Note: there are other questions on StackOverflow about durable renames, but AFAICT they don't address fsync-ing the directories (which is what matters to me - I'm not even modifying file data). I currently ha...
Let's say you're building a journaling/write-ahead-logging storage system. Can you simply implement this by (for each transaction) appending the data (with write(2)), appending a commit marker, and then fsync-ing? The scenario to consider is if you do a large set of writes to this log then fsync it, and there's a failure during the fsyn...