I've been having problems with my external hard drives for a while. A few days ago I described the new setup I'm putting in place. I still have to build an external RAID-0 setup for backup, using TimeMachine. With the joy of my new Hitachi disks, I didn't INVEST the time to thoroughly test them, but I'm doing that now with my backup disks.
- a full scan of the surface of the disks, ie. testing that you can write and read back every block on the disks. My test on a 2 TB disk from LaCie using a Firewire 800 connection took about 17 hours... and I did find 11 bad or suspect blocks, which is to say close to 0%. But if that falls on an important file, you loose the file. I use Drive Genius 2 for this.
- the only way I've found to solve that easily is to TOTALLY reformat the disk, with a Zero Out option (ie. writing data to each block, so that the system detects again bad blocks). It's going to take at least 7 hours (it's now reporting 10 hours to go...). I use Disk Utility for this. This guy describes a faster way, but I don't want to mess up with sectors in Hexa (that was one of my engineering degree exams... analyse a core dump :( Maybe Apple will implement ZFS as a successor to HFS+ ?
- of course, once the formating is done, re-scan the whole disk (17 hours...) to check that the surface scan is now OK ... otherwise It's probably either wiser to repartition the disk and leave the bad blocks in the bad partition, or just discard the disk. The value of my data is not worth trying to salvage one disk.
- I then need to test 9 more external disks... and figure out how I'm going to stress test my 5 internal disks if I really want to be safe... takes forever :(
Data safety is not an easy problem, and I wish there were real solutions out there, including full online hosting for my disks when fiber gets to my place. Any joyful entrepreneur up to the task ?
Screenshots of work in progress :