From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stan Hoeppner Subject: Re: Suboptimal raid6 linear read speed Date: Sat, 19 Jan 2013 16:48:56 -0600 Message-ID: <50FB22D8.5000803@hardwarefreak.com> References: <20130115123301.GA11948@rabbit.us> <50F55046.7050605@turmel.org> <20130115125507.GA12184@rabbit.us> <50F614F7.20104@hardwarefreak.com> <20130116025857.GA31112@rabbit.us> <50F70DB7.6020104@hardwarefreak.com> <50F90857.3010305@hardwarefreak.com> <50F9D32F.7090606@hardwarefreak.com> Reply-To: stan@hardwarefreak.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Mikael Abrahamsson Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 1/19/2013 1:43 AM, Mikael Abrahamsson wrote: > With a BER of 10^-14 you have a 16% risk of getting URE when reading an > entire 2TB drive. On 1/19/2013 7:21 AM, Roy Sigurd Karlsbakk wrote: > ok, perhaps, maybe, but then it's 17% chance of losing data after a > mirror or raid-5 rebuild with 2TB drives... Where are you guys coming up with this 16-17% chance of URE on any single full read of this 2TB, 10E14 drive? The URE rate here is 1 bit for every 12.5 trillion bytes. Thus, statistically, one must read this drive more than 6 times to encounter a URE. Given that, how is any single full read between the 1st and the 6th going to have a 16-17% chance of encountering a URE for that one full read? That doesn't make sense. -- Stan