I/O Errors - what are they and how to fix them?

Only if you post the relevant errors.

Hi--

I/O errors are caused by different problems. First, they can be caused by physical problems with the disk, i.e., a problem with the media on the platter of a hard drive, also known as bad blocks. They can also be cause by faulty cabling, either defective cables or cables that aren't properly seated. Finally, they could also be caused by a faulty drive controller, the chip that translates the commands from the OS to the disk drive.

One thing you can do is look in your Console application (from the Utilities folder) at the console and system log. When you get a disk I/O error, look in there and see which disk has the error. It will be a little cryptic, with the BSD identifider, usually something like "disk0s9", though the numbers will change. Then you can look up that information in the Disk Utility program. Just click the name of each volume, (not the name of the drive) and get info to look up the identifier.

You can also get the list of disks a bit easier by opening the Terminal app and running this command:

<pre class="command">diskutil list</pre>

You'll get a list a little bit like this:

/dev/disk0
 #: type name size identifier
 0: GUIDpartitionscheme *232.9 GB disk0
 1: EFI 200.0 MB disk0s1
 2: Apple_HFS Macintosh HD 94.9 GB disk0s2
 3: Apple_HFS Partition 2 14.9 GB disk0s3
 4: Apple_HFS Partition 3 122.6 GB disk0s4
/dev/disk1
 #: type name size identifier
 0: CDpartitionscheme Live At Leeds [Deluxe Edition] *742.1 MB disk1
 1: CD_DA 51.7 MB disk1s1
 2: CD_DA 32.5 MB disk1s2
 3: CD_DA 26.1 MB disk1s3
 4: CD_DA 37.4 MB disk1s4
 5: CD_DA 62.5 MB disk1s5
 6: CD_DA 21.4 MB disk1s6
 7: CD_DA 22.5 MB disk1s7
 8: CD_DA 78.5 MB disk1s8
 9: CD_DA 89.6 MB disk1s9
 10: CD_DA 34.0 MB disk1s10
 11: CD_DA 46.2 MB disk1s11
 12: CD_DA 159.6 MB disk1s12
 13: CD_DA 80.0 MB disk1s13

That's what I see on my computer where I have the main hard drive partitioned into 3 parts, plus a CD inserted.

Once you know where the errors are happening, you can track them down by determining if it's a write operation or a read operation causing the error. Also, see if you can narrow it down to a single file or files.

charlie

Hmm. First off, the I/O error is on your "LaCie 500G 2 (new)" disk, so are you trying to copying to or from that disk?

The simplest way to see if you can fix it is to reformat that drive and choose the option that writes zeroes to the drive. That should map out bad blocks, if there aren't too many. Unfortunately, I'm not sure of a way to check if it was successful with an external FireWire drive. I don't know if TechTool Pro will do that or not (I kind of doubt it).

If it's a read error on "LaCie 500G 2 (new)" you might be able to get around the error, but you'll have to determine if it's one file or a bunch of files. The only way to do this is to try copying them to another disk using the Finder and see if you can determine which files have errors. If you get a bad file, try copying it a couple of times to make sure it fails in about the same spot. Then you know it's a physical problem with the drive. If different files have errors at different places, then it's more likely the cable or the electronics in the drive.

If you can find the bad file, you might be able to work around it by not deleting it and re-capturing it with Final Cut. As long as the OS doesn't have to read that file, it shouldn't matter. But that's only a short term solution.

A write error is going to be harder to work around, since I don't know of a way to control where the files get written on the HD.

Finally, as far as de-fragging, I don't think that's your problem. Fragmentation would only result in dropped frames, but not I/O errors. I/O errors are more serious errors reported back to the OS by the drive's firmware...

charlie