So in the past 24 hours I've been trying to upgrade my internal hard drive from 320GB to 1TB. It's a little more complicated than usual, because I have a SSD as my primary drive, and the mechanical drive is in a caddy in the optical bay. It's also more difficult because I don't have a built-in super drive any more, and the external DVD drive I normally use stopped reading DVDs (it still reads CDs just fine), so I can't boot from the install disc. So I put the new drive in an enclosure and tried to use Disk Utility to restore to it from the existing 320 drive. The first time it failed about half way with a vague error that said something like input/output error. I think it was trying to do a file-level copy, and the source drive was still mounted the whole time. The second time I quit everything and tried again, and it unmounted the source drive and did a block level copy. It took about 6 hours (I let it run overnight), but it appeared to work. In the morning all the data appeared to be there, and I simply had to recreate my sym links to make everything work. However, when I started to use it, I noticed that many of my files were corrupted. I noticed it mainly with image files, but I didn't spend a lot of time trying to test various kinds of files, and I neglected to do a ckecksum on any of the corrupted files. The specific problem was when I tried to open a corrupted image, Preview would say that it does not appear to be a valid file, or something like that. Rather than risk having the corruption somehow affect data on my SSD (for example, if I tried to open a program with a database that points to corrupt files, the program might decide to delete the database), I tried restoring from my Time Machine backup. That too, appeared to be successful, but it looks like it didn't quite get everything because the number of files and the space used on the drive is now slightly lower. I know Time Machine won't back up caches and temporary files, so maybe this is OK. I plan to try to run a script to compare the contents of the old drive to the new one at some point. So I'm wondering about the corruption after the block copy, because I haven't seen anything like it before. Only some files were affected, but it looked like a significant portion of them (maybe 20%). Could the problem be caused by the fact that the new drive is an "Advanced Format" drive with 4K sectors? Everything I read says OS K supports those with no problems. I'm running 10.6.8 on a MBP4,1 with a 60GB SSD in the normal spot, and the new drive in the optical bay with a PATA-SATA conversion caddy. Aside from the new drive, nothing else has changed and I've been using the same hardware setup for at least a year with no problems.