Hi, i wrote my own file device to get large file support on windows without the system caching the file. now, when i use this device with boost::iostreams::stream or stream_buffer all read and write access is buffered (default 4096). i found the suggestion to create the stream or stream_buffer with a buffer size of 0, but then the access to the read or write function of the device are always for 1 byte. what can i do to get real unbuffered access to the device. another problem. i use the device with the default buffer size of 4096. and access it like follows: boost::iostreams::stream<mydevice> ifile; char* buf = new char[3200]; for (int i = 0; i < 100; ++i) { ifile.seekg(32 * i, std::ios_base::beg); ifile.read(buf, 32); } now with the first read the buffer of 4096byte is filled up. then i seek 32 byte into the file and the next read operation AGAIN reads from the device? why buffer when this case it not caught? i am using boost 1.35. regards -chris -- Christopher Lux | | Bauhaus-Universität Weimar | faculty of media - virtual reality systems group