On Nov 28, 2012, at 12:18 PM, Roy Sigurd Karlsbakk <roy@xxxxxxxxxxxxx> wrote: >>> That doesn't make sense. Nearline and enterprise drives are large >>> 7k2 drives that come in consumer and enterprise models, >> >> Nearline drives are in between consumer and enterprise. > > Well, they are named enterprise… Yep it's misleading. SNIA has a slide show describing the differences between consumer nearline and enterprise. > 7k2 "nearline" SAS drives exist from several vendors, with SAS interfaces without the need for adapters. Also, the interface, wheather SAS or SATA or FC, doesn't really mean much when the drive is the same. SAS (and FC?) has better timing and better controllers, but a SAS drive is a SAS drive nonetheless if it has a SAS interface. Nearline SAS is effectively a consumer SATA drive (you don't get the better mechanics), with a SAS interface. > Then, if this is true, perhaps they should name their 4TB drives something else than "enterprise", which they do. Do you have more references on this part? Basically you have to look at the specs. Maybe a reasonable rule of thumb is the URE, but even that gets perverted sometimes. < 1 bit in 1E14 is consumer, 1E15 is nearline, 1E16 is enterprise. For example: http://www.wdc.com/wdproducts/library/SpecSheet/ENG/2879-771386.pdf <10 in 10^16 = <1 in 10^15, means this is nearline. It's clearly the same as the RE SATA in every way (all mechanical specs) except that it's a SAS interface. Whereas this: http://www.wdc.com/wdproducts/library/SpecSheet/ENG/2879-771429.pdf <10 in 10^17 = <1 in 10^16 is enterprise. Notice the size and speed difference, which is where "nearline" is being used. More capacity and slower than enterprise makes it nearline, more so than the URE. But URE makes it easier to distinguish between consumer and nearline. Chris Murphy-- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
