I use USB Flash Drives, a USB Memory Card adapter, a USB wireless mouse, USB connected DVD / CD Drives and a powered 9 port USB hub (made necessary by the DVD / CD Drives which are normally not plugged in when not in use).
This is despite the fact that I have always found USB to be somewhat erratic and unstable
A nagging problem I frequently experience is, especially when i start up, I cannot get the USBs to connect (hand-shake) right away. This often requires me to remove / reinsert the plug from its USB socket several times (sometimes many times). It is especially bothersome with the mouse, as I cannot properly get going until it starts to respond --- I only use the pad and touch to a limited extent, I feel handicapped without a mouse. I also think it must not do the physical connections much good. And of course from time to time the Flash Drives get corrupted, so I cannot rely on them for secure storage. I have accumulated about 6 'dead' USB Flash Drives over the years. I had hoped the powered hub would reduce the problem but it has not done so.
All this is in marked contrast to my integral SD Memory Card which has never been any bother since first installed over six months ago. Now to come to my questions:
1. If I have to use the ISO / bootable USB media route for the upgrade to Windows 10, is there any reason why I cannot use a more reliable high capacity integral Memory Card, instead of a Flash Drive or DVD? Are DVD discs large enough anyway at just over 4 GB?
2. Will it be a good idea to use the more reliable Memory Card for backing up my Windows 8.1 OS rather than USB Flash Drive? (I do already have a Recovery USB Flash Drive --- is this all that is required? Also I have Norton Backup online as well, so do I need another backup too?)
3, How do I find out how many GBs I will need for each of these operations?