Printed 2017/07/23 03:36AM

ZFS & Hard Drive Defects

By Andy Warren, 2007/10/21

The most recent ACM Queue Magazine (Vol 5 #6, Sep/Oct 2007) had two really interesting articles. The first was about the ZFS file system and was framed as an interview it with the two inventors, both from Sun. I'd seen it mentioned a few times via blog and took the opportunity to learn more. It was interesting to hear that they built the file system to expect hardware errors, to never require a disk check, that they think storage really should be a pool that you can just add (much like a SAN, but at the file system level). They talked about the fact that all drives have defects at start and that errors are always occurring, its just a matter of which ones get passed up to the OS. You can see the article at The second article (same issue) was about HDD's and was written by Jon Elerath of Network Appliance and really went into detail about how drives map and remap to handle errors, how the SMART functioin of drives isnt necessarily that smart, and some other good stuff too! More and more DBA's are insulated from storage but I think its a good idea to have a least some of idea of whats happening in the storage industry and how it relates back to us.

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