No, I don't need files, FAT, etc! 
I just wanna use SD card like a piece of memory, or memory space.
Is it unreal too?

No, I'm talking about approach of using SD via linear memory space.
For example, ((*byte)EEPROM_Base+Offset).  Similar approach is used to access external RAM, after enabling this one in MCU regs.

What about technique of memory-mapping?
Can I write (or read) data to (virtual base pointer + offset) to except SDfat approach at all?   Just memory operations without files etc.

Hi guys!
My device has SD-card datalogger, but there is periodically data lost while this one works:

Datalogger uses SD.h. 2GB SD is connected via SPI.
How can I write data without FAT (using SD as memory block)? 
Or maybe is there the "fast FAT" version of SD.h?
Now speed of data write is about 25Hz, but I need 100Hz+.
Please help to decide this problem.