Highly Reliable Systems: Removable Disk Backup & Recovery

Tag Archives: Bit Error Rate

Why RAID-5 Stops Working in 2009 – Not Necessarily

Posted on by Darren McBride

Suppose you were to run a burn in test on a brand new Seagate 3TB SATA drive, writing 3TB and then reading it back to confirm the data. Our standards are such that if a drive fails during 5 cycles we won’t ship it. Luckily, all 20 of 20 drives we tested last night passed. In fact, most of the 3TB drives we test every week passed this test. Why is that a big deal? Because there is a calculation floating around out there that shows when reading a full 3TB drive there is a 21.3% chance of getting an unrecoverable read error. Clearly the commonly used probability equation isn’t modeling reality. To me this raises red flags on previous work discussing the viability of both stand alone SATA drives and large RAID arrays. Continue reading

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