Memory and other upgrades for photo editing

So I have hard, and I believe you, but why should that be?

I have always thought of ssd memory as nothing more than what it says - solid state memory and, as far as the OS is concerned, exactly the same as hd memory except for the low level routines which actually read and write the data. Further, ssd memory would be addressed by the OS exactly as hd memory would be through a FAT of some kind. When new data was written the appropriate space would be found through free memory. If that memory was contiguous, great. If not, well that is what linked-lists are for.

Given that I don't see why ssd memory would not fragment the same way as hd memory does.

There are two possible caveats:

1) Some users, like myself, might choose to store only the OS and apps on the ssd and to store all app data on a separate external usb drive. That sound good. Apps are less likely to cause fragmentation because they are less likely to be deleted and recreated as data often is. But the reality of the fact is that apps do get deleted and apps often re-write their own app data separate and distinct from where the user might think the app data is being stored. Thus config files, startup files, hidden data bases and the like might often get deleted and re-written and I don't see why that would not also cause fragmentation. And

2) It is possible that ssd have built-in defrag programs since memory speed is so fast compared to hd speed. Perhaps the ssd is constantly undergoing de-fragmentation. If that is the case, then I would assume that the memory would be relatively contiguous, but I would also assume that the cost in memory cycles would be significant and it is hard to see the system doing that well without some impact to memory intensive apps.

Maybe I am missing something here but I don't see why ssds would not become fragmented. Perhaps you can clarify. Ssds are not main memory where programs are loaded and unloaded so I just don't see why they would not become fragmented.