Is this drive failure or something else?

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http://askubuntu.com – I have a year-old drive that's giving me trouble. Copying data to it fails after about 8-10GB of transfers. It spontaneously changes to 'read only'. It's properly formatted ext4, I'm the owner. Searching online, it looks like this is a symptom of a failing drive. How do I confirm this, since the SMART tests indicate otherwise? I did the obvious like check the Disk Utility, and ran the extended SMART test. All results from Disk Utility come back perfect. Read error rate and reallocated sectors are showing zero. I'm guessing this disk is bad and SMART isn't detecting it, though I don't und (HowTos)