FAT May Be Exchangeable but Still Not Your Friend

Posted by: Thom Denholm

Open the box containing your new electronic device and you can count on the presence of one other item tucked in under the plastic bags, tie wraps, and tiny, barely readable user manuals: the umbilical cord. According to a recent Nielsen/Netratings report, 89.4% of us connect our gadgets to a Windows host machine, underscoring how crucial it is for manufacturers to consider file system compatibility with the Windows desktop. The ubiquity of the FAT (File Allocation Table) file system makes exchangeability easy for those of us who create embedded designs, but FAT is also the cause of a lot that goes wrong with these devices. If you design embedded systems for a living, FAT is like a friend who is always there for you, but who undermines your most brilliant work and holds your designs back from embedded greatness. FAT, oft updated since being developed by Bill Gates and Marc McDonald for late 1970's desktop computing, still uses the same basic architecture. As a result, many of its original problems are still with us. For designers in the embedded space, the quirks of this clunky and aging file system are familiar and particularly problematic: corruption when power is cut, excessive fragmentation causing slug-like performance, and wasted disk space due to inefficient memory allocation. Corruption on FAT is especially noticeable on removable media when the media is removed while write operations are happening. Reliable, better performing options such as ext3 are out there, but files are not useable by a Windows host machine, a deal breaker for most embedded OEMs (remember the 89.4%?). At Datalight, we've addressed the issue with our Reliance file system and a simple driver called RWD (Reliance Windows Driver). Once loaded on the host machine, RWD allows Reliance-formatted media to be read and used on the Windows host. With Reliance and RWD, OEMs and their customers no longer have to choose between reliability, performance and exchangeability. Check out the press release announcing our new RWD version 2.0 with support for Windows Vista.

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