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-   -   recovering from i/o error (http://www.shirt-pocket.com/forums/showthread.php?t=6781)

camner 03-22-2013 04:45 PM

recovering from i/o error
 
Yesterday I cloned one external drive to another external, and just about the same time that SD finished up, there was a spontaneous unmount of the target volume. This has happened to me before (occasionally) and I was successfully able to redo the cloning (using Erase and copy, not Smart Copy).

I then repartitioned the 1st drive and started to clone back. Consistently (I've tried cloning back several times) there is an i/o error which I'm pretty sure is on the drive being read (that is, the TARGET of the initial clone yesterday that is the SOURCE of the "cloning back" process). I say "pretty sure" because I found a reference in the Console logs to an i/o error on "disk1s2" and using disk utility I could tell which volume was "disk1". [By the way, is there any easier way to find the i/o error than looking through lots of log entries in the 'all' log entry...such as a particular log to look at?]

I've swapped the drives physically (I have two Voyager docks) to try to eliminate the possibility that there is a cable or physical problem with the dock and the problem persisted in the other dock.

What I'm going to try to do is to use the Finder to copy a smaller number of folders at a time rather than SD to try to clone the entire disk. Fortunately, it isn't a volume that contains a system!

So, a couple of questions:

1. Is my proposed approach a reasonable one? Can I count on the Finder copy being reliable if I don't get a read error?

2. Once I've gotten this read error, should I presume that the drive is toast, or is there a way to check the drive (and perhaps remap the bad sectors, if that's what it is)? It's not a new drive, and if it makes more sense to trash it, I'm certainly open to that!

Thanks!

dnanian 03-22-2013 08:20 PM

The error is usually pretty clear and tells you if it's a read or write error. If you're getting errors of this sort on the drive, and it's not the case or cable, I'd replace the drive.

camner 03-22-2013 08:23 PM

Thanks for your response. As it's a 5 year old drive, I think I'll go the replacement route.

sjk 04-08-2013 01:19 PM

Quote:

Originally Posted by camner (Post 32310)
[By the way, is there any easier way to find the i/o error than looking through lots of log entries in the 'all' log entry...such as a particular log to look at?]

With Console, you could run File > New System Log Query (Option-Command-N) to create a simple query like:
https://dl.dropbox.com/u/71730/Super...20Messages.png
Or run this shell command:

Code:

bzgrep 'I/O error' /var/log/system.log*
Or do something similar with the syslog command.

None of those methods alerts you of errors when they happen, as utilities like SMARTreporter or a wrapper script for the aforementioned commands can. And I think SMARTreporter can keep a history log of events that's retained longer than the default system logs.

dnanian 04-09-2013 10:23 AM

Note, too, that some I/O errors do not log to the system log. Why? Who knows...


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