Microsoft's embedded range of operating systems brings many benefits to computers operating in the vehicle environment, including:
At In-CarPC we have experience in planning, preparing and deploying embedded operating systems. We can work with you at whatever level you require – from simply providing sample hardware to assist you in creating your embedded operating system image yourself (which we can then deploy to each PC you order), right through to creating the entire system for you, complete with your software and configured to your liking.
Please note that creating an embedded operating system image is a non-trivial process, and is not something we would recommend for low volume orders.
As mentioned above, a key advantage of using an embedded operating system is that the system can be hardened to be tolerant of improper shut downs. Although hardware features like the internal back-up batteries on our CQ family PCs can help to prevent improper shut downs, use of a hardened operating system can be a more cost effective solution.
Tolerance against improper shut downs is achieved through a technology known as write filters. The write filter can be thought of as a buffer that lies between the computer's hard drive or SSD and the rest of the system.
A normal desktop operating system constantly writes information to the hard drive, even when appearing to be idle. If the PC abruptly shuts down while a file is being written to the drive (e.g. as a result of the vehicle’s master switch being turned off) this is likely to result in file corruption. If that corrupted file is a critical operating system file then the operating system may fail to boot when the PC next turns on.
In an embedded operating system with a write filter enabled, it is possible to ensure that no data is ever written to the drive. Instead the write filter keeps track of all these drive writes in the PC's RAM, a process which is completely transparent to any programs installed on the PC. When the PC shuts down – either normally or abruptly – all these changes are lost. The next time the PC boots it remains in exactly the same (working) state that it was in before.
There are various different types of write filter, and the above description is based on Microsoft's Enhanced Write Filter (EWF) protecting the main operating system partition (normally drive C:\). The EWF acts at the partition level, protecting the entire partition from changes. Clearly there will often be cases when the PC needs to retain data between power cycles, and this is normally achieved by setting up a second partition (e.g. drive D:\) and applying a different type of write filter – the File Based Write Filter (FBWF) – to this partition.
The FBWF protects at the file level, and allows certain files to be excluded from the write filter (i.e. to be writable). Any data that needs to be retained through power cycles (e.g. configuration files or log files) would be stored on the D:\ partition, and these files added to the FBWF's list of excluded files. Of course, it is possible that these data files could be corrupted, but writes to these files are likely to be much less frequent than operating system writes, and in any case sensible software design can prevent data file corruption from bringing down the system (e.g. by having a set of "default" files stored on the EWF protected partition, which are copied over to the FBWF partition if they become corrupt).
A combination of the EWF protecting the operating system partition, and the FBWF protecting the "data" partition, ensures that the operating system itself and any programs are fully protected against file corruption due to improper shut downs, while still allowing important data to be retained between power cycles.