disk flaws, classic vs. modern

I have a problem that cropped up that spans both old systems and flaw maps / disks that have flaws to skip over and current technology. In the old days with my experience on a lot of cdc winchesters and removable pack smd drives (and trident) there were flaw maps you could use in a controller to figure out where the bad spots were. When shipped from the factory the mmd / cmd / emd / fsd drives (at least the first two) were not allowed to have more than a false address mark on a track, and a limit of maybe 5 for the entire stack. Later at least on the mmd's they had run of marginal media and upped the FAM errors considerably. (10? 15? don't recall). I later found some drives delivered to such as Datapoint for large systems delivered when we got the story about the FAM problem (needing to up the count) that had zero flaws, but that was 10 years later buying some scrap drives (better than the ones I had purchased 10 years before, still working). Anyway, recently I had a system with a 1.5tb seagate grow a count of "uncorrectable offline sector count" errors. I'm telling this up front since these are effectively the same as the above errors, sectors that are not recoverable by the drive and presented as bad or timeout spots when you seek to the sectors. The errors were not there when I initialized the linux system on the drive, and grew later. To complicate things a bit this was part of a LVM raid ext3 raid 5 set, so there are other complications here, but the initial build was flawless, ran about a 6 months then this drive grew 16 bad errors visible to linux. So, I have now got the situation where there is a bad spot in a file (more complicated because this is part of a raid set, but bear with me). If you power cycle the drive set they do a scan of the media with the raid system I'm using (linux based) and hang before releasing it for server operations. That is the only flaw that there was, and I had a brick. Thank heaven I could put it in a desktop system and recover the data (7tb of it). Anyway, have we lost the capability with such as Linux to run with flaws growing on media at the level where transfers from media come from the drive target to the host, or did this vendor of raid equipment (appliance was readynas nv2+) have a flaw in their bringup procedure. I am glad I shopped and got a system with raid 5 support like this with a linux system that I could take out and troubleshoot with any linux tools, rather than hardware raid. Dodged that bullet. but I am disappointed even so with the behavior of the raid set when I put it on my recovery system. I think there is a basic loss of what one would have been accustomed to in earlier times with media, throwing their hands up with defective media. I was only able to narrow down the error with manual applications of careful dd commands and shell scripting (lacking a better tool) to see the errors. There is a nice timesaving web page if you hunt around the pages found by searching for smart errors. At least that is a nice tool, telling a lot about the drive. I am not going into why a 1.5tb drive with huge amounts of extra space (as I understand it probably > 500gb) can't reassign media 16 consecutive sectors, as that is a totally different discussion. Jim