OS X Mavericks doesn't read my external hard drive

That would be nice, but they run about $100 each. If I could only pick one it would pick DiskWarrior. Then I see what I could find that scanned disks for bad blocks.

I’m just guessing here, but I suspect reconnect and disconnect are mount and unmount. If I’m right, you’re having problems dismounting a drive. Common problems that prevent unmounting are open files, not usually the problem if booted from the recovery disk, or damaged directory structure. Why one OS would choke on the disk and not the other is a mystery.

So far I’ve had no problems with drives on Mavericks. I currently have 4 external drives on my Mac, two Seagates, a Toshiba and whatever Buffalo puts in their cases. I’ve also used Western Digitals, another Seagate, another Toshiba, an Envoy case containing the original SSD from my MacBook Air and a Thunderbolt SSD who’s name escapes me. Not one problem. The only thing was the drives were all partitioned with GUID and formatted HFS+ and no third party drivers or any software from the drive manufacturers was used.

Now I have had drives that didn’t work, but that was due to a directory or partition table being damaged by a bad block.

Bad blocks in the directory structure renders a HD useless. Many files may yet be recovered, but it’s sure death for the drive. TechTool Pro has a utility that makes a copy of the directory and periodically stores it on other drives just in case this happens, which sounds like a pretty neat idea, but I haven’t had a chance to try it out yet.

I was just reading that thread.

Do you have any third party software from the drive manufacturer installed?

The reason I asked was that WD ncluded software on their drives that caused file loss under Mavericks.

I'd love to do a surface scan on your drive, once on tthe old machine and once on the new.

Here's a list (link) to most of the drive and system related tools available, both free and commercial:

Mac Hard Drive and System Test Tools

As an FYI, or in this case, guess, you might want to contact the manufacturer of the drive and see if it's Mavericks compatible. Since Mountain Lion, external drives seem to be finicky and the OSes no longer seem to be as "friendly" as they once were.

Mac OS X is a Unix operating system. What you're seeing are the "user friendly" presentations of Unix file permissions, user, group, and other. Since you're marcoguasc... unless the user name and ID have changed, then that's basically saying you have permissions to access the drive.

I'm inclined to think it's a drive compatibility issue. With one of my external drive, Mavericks more or less dropped it, then said it couldn't be read and it needed to be reformatted. Fortunately I had a Lion volume around so I booted from it and ran Disk Utility to repair the drive, which it did.

One thing I've noticed is that some people need to disable the "Put hard disk to sleep when possible" option under System Preferences -> Energy Saver options. I'd be surprised if that was the issue but it's worth a try. Another thing you might try is to reset the NVRAM:

http://support.apple.com/kb/ht1379

with the unit plugged into the new computer. Once again, I'd be surprised if it works, but it might be worth a try.

The two problems I can think of are that the drive has an incompatibility issue, and possibly some type of problem with the use of the DOS file system.

I've been using Macs for 20 years and have never come across a drive that wasn't able to be used with a Mac. This includes Syquest, Magneto-Optical, Zip drives, flash drives, SCSI, USB, Firewire and now Thunderbolt.

Now I've come across my share of defective drives, I even had one fry my motherboard, but replacing the drive with a working duplicate always worked.

What exactly makes a drive incompatible with a Mac? I do recall SCSI being touchy, but since SCSI was dropped anything that could be used for Windows could be formatted for Mac use.

At least this has been my experience.