On Fri, Jul 5, 2013 at 1:37 PM, David Lum <[email protected]> wrote: >> Be careful of a SATA Raid array. I've got a couple of these and in an >> effort to save money and I'm not doing it again. The issue comes down to >> something I learned about the hard way. "Array Puncture"... > > I have never heard this term before today, looking it up now.
Me neither. This explains it: http://www.dell.com/support/troubleshooting/us/en/04/KCS/KcsArticles/ArticleView?c=us&l=en&s=bsd&docid=438291 Nothing to do with SATA, it appears. It's just a fallback method for a double fault. A double fault is when two blocks (stripes) are both found to be bad. This is more than a RAID 5 can tolerate. A "puncture" appears to just be an option to keep an array operating despite a double fault. You've got two choices when you encounter a double fault, fail the entire array offline, or "puncture" it, rebuilding what you can, and returning error on those particular blocks. The double fault problem has been known for decades, and is why better RAID implementations do regular consistency checks across all disk members. -- Ben
