I think I would find a "Try to keep files in directory X on disk Y" or "Try to keep directories together (In general or below file or directory size Z)" option extremely useful.
Hypothetical Situation: I have a bunch of ripped CDs stored on my home server. It's a directory (named Music) of many smaller directories (named Album Title) made up of smaller files (Each Song). DrivePool spreads these songs evenly between my two drives. If one drive dies, I could quite possibly lose half my songs from every album, meaning I would need to re-rip all of my CDs to restore my collection.
Ideally I would have easily accessible backups, or have DrivePool set to keep multiple copies of everything, but that does not always happen. I don't mind taking a calculated risk for some low priority files, but I would still prefer to minimize the amount of work it takes to recover from a failure.
In my view, for sets of files that depend on each other, my exposure to damage to the set goes up the more dispersed the set is. Meaning that for non-duplicated sets of files, DrivePool could be riskier than non-pool storage. In the above example, a single drive failure could damage all of my albums. If my music storage was clumped by album, worst case a single drive failure would cause the complete loss of half my albums.
Both failures involve data loss, but depending on the situation, one can be much more painful than the other to recover from. Even with backups.
I'm relatively new to using DrivePool. Does DrivePool have a way of keeping track of what files are on what drive, so in the event of a failure, I could figure out which sets of files (or albums) were affected? Or do I need to be keeping track of that on my own? For the most part its easy to tell if a data set is whole, but some things are harder than others. Using the music example, It's easy to tell if a track in the middle of an Album is missing, but less easy to tell if the last track disappears.