On 2013-11-04, John R Pierce pierce@hogranch.com wrote:
On 11/4/2013 9:30 AM, Les Mikesell wrote:
Besides, if you have a problem with a truly humongous RAID, the rebuild
will finish sometime around next summer....
Yes, I'd probably use a RAID10 style RAID so it runs at full speed even with a drive out of the array so you can put off the rebuild until a weekend. A rebuild will keep the heads too busy to do a lot of other work while it is running.
Using a common LSI Logic Megaraid card (9260-8i, I think, but don't quote me), and 11 by 3TB raid6 with hotspares (using Seagate Constellation.ES2 SAS2 drives), single drive failure rebuilds took 24 hours, double drive failures took 36 hours, this with the system online but mostly idle the whole time. yes, if you have steady user IO activity going on the rebuild would take quite a bit longer, as it only proceeds when the disks are idle.
The MegaRAID controllers have a configurable rebuild rate. The default is 30%, but you can increase it up to 100% (which will probably kill your system IO). LSI 3ware controllers are also configurable in a similar way (their scale is only 1..5).
--keith