HELP! Both Raid Drives "not readable"

Started Apr 2, 2013 | Discussions thread
Jacques Cornell
Jacques Cornell Veteran Member • Posts: 8,423
Secure erase / surface scan

Joe Tam wrote:

Thanks.  I formatted the drive that was displaying the errors now that I restored the data.  Is there any way to tell if it was a physical error?  I ran test disk and I think it was a partition map error?  Can formatting the drive restore the drive?  Or should I just send them back to Hitachi under warranty?

If it's under warranty, yes, I'd send it in for replacement. Now, there's one other thing you can do to protect yourself when you get a new drive or to repair a drive that may have damage on the platters, and that's to do a "secure erase". I do this on every new drive I get before I put it into service. You see, the magnetic recording material on a platter may have or develop over time defects at some physical locations which render it unable to reliably record bits of data at those locations. Doing a secure erase forces the drive to write and test data at every single bit. When the drive finds a bit that cannot be switched back and forth between 1 and 0, it logs that location and removes it from the map of blocks available for storing data. On a Mac, you can use Disk Utility to do a Secure Erase, or you can use a utility like Drive Genius or TechTool Pro to do a "surface scan".

Most data "loss" is simply corruption of the directory file that tells the OS where files are stored. However, when directory repair doesn't work and a drive is hosed, I've found on occasion that, after recovering the data, I could restore a drive to service by performing this secure erase / surface scan.

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