At that point the RAID reconstruction stops.
As the RAID controller is reconstructing the data it is very likely it will see an URE. When a drive fails in a 7 drive, 2 TB SATA disk RAID 5, you'll have 6 remaining 2 TB drives. Which means that once every 200,000,000 sectors, the disk will not be able to read a sector.Ģ hundred million sectors is about 12 terabytes. SATA drives are commonly specified with an unrecoverable read error rate (URE) of 10^14. The problem with RAID 5 is that disk drives have read errors. The extra bits - parity - enable the lost data to be reconstructed by reading all the data off the remaining disks and writing to a replacement disk. The crux of the problem RAID arrays are groups of disks with special logic in the controller that stores the data with extra bits so the loss of 1 or 2 disks won't destroy the information (I'm speaking of RAID levels 5 and 6, not 0, 1 or 10). More good news: one of them already has - and I'll tell you who that is. The lead time may be shorter unless drive vendors get their game on. Leventhal assumed that drives are more reliable than they really are. Leventhal found that RAID 6 protection levels will be as good as RAID 5 was until 2019. He lays it out in the Association of Computing Machinery's Queue magazine, in the article Triple-Parity RAID and Beyond, which I draw from for much of this post. Late last year Sun engineer, DTrace co-inventor, flash architect and ZFS developer Adam Leventhal, did the heavy lifting to analyze the expected life of RAID 6 as a viable data protection strategy. Instead it is due to the increasing capacity of disks and their steady URE rate. RAID 6 in a few years will give you no more protection than RAID 5 does today. The power of power functions I said that even RAID 6 would have a limited lifetime. But in 2019 even RAID 6 won't protect your data. They now recommend RAID 6, which protects against two drive failures. Sure enough, no enterprise storage vendor now recommends RAID 5. Three years ago I warned that RAID 5 would stop working in 2009.
0 kommentar(er)
