Rob Cole wrote:
...what I said was that files can become corrupted under Lr's watch due to faulty hardware (e.g. bad ram), when embedded xmp is being saved, due to the fact that the entire file sometimes gets re-written, image data and all - if you think otherwise, then you think wrong.
The entire file (including image data) get's rewitten? You think that? Then you don't understand the way .xmp is written to the headers of files. Those headers reserved for .xmp metadata have built in padding to allow for the expansion of new additional xmp data. It may be that if a header gets too full, the headers will be rewitten to expand the header padding. At no time (that I'm aware of) does that require rewritting the image data in the file. Can corrupt header data make the image inaccessable? Perhaps...I've never seen a case of that. Have you?
Lightroom does load the entire image into Lightroom when working in the Develop module...but the only thing LR alters in Develop is the xmp settings, not the original image data.
What I have seen is image corruption happening because of faulty cards, faulty writting to the card from a camera, faulty cabling when trnasfering the image to the HD or a faulty card reader. I've also seen image corruption caused by failing hard drives (files there were good becoming corrupted or unreadable due to loss of data ingetraty on the drive). I've seen images corrupted by faulty ram in Photoshop (but never in Lightroom).
You'll note that DdeGanes image corruption was being caused by faulty ram but the images were corrupted during an import (copy) process...not once the images were safely copied to the HD...