On Wed, Nov 20, 2013 at 10:52 PM, Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx> wrote: > On 11/20/2013 8:46 PM, John Williams wrote: >> For myself or any machines I managed for work that do not need high >> IOPS, I would definitely choose triple- or quad-parity over RAID 51 or >> similar schemes with arrays of 16 - 32 drives. > > You must see a week long rebuild as acceptable... It would not be a problem if it did take that long, since I would have extra parity units as backup in case of a failure during a rebuild. But of course it would not take that long. Take, for example, a 24 x 3TB triple-parity array (21+3) that has had two drive failures (perhaps the rebuild started with one failure, but there was soon another failure). I would expect the rebuild to take about a day. >> on a subject Adam Leventhal has already >> covered in detail in an article "Triple-Parity RAID and Beyond" which >> seems to match the subject of this thread quite nicely: >> >> http://queue.acm.org/detail.cfm?id=1670144 > > Mr. Leventhal did not address the overwhelming problem we face, which is > (multiple) parity array reconstruction time. He assumes the time to > simply 'populate' one drive at its max throughput is the total > reconstruction time for the array. Since Adam wrote the code for RAID-Z3 for ZFS, I'm sure he is aware of the time to restore data to failed drives. I do not see any flaw in his analysis related to the time needed to restore data to failed drives. -- 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
