From owner-freebsd-questions@freebsd.org Fri Mar 17 10:01:42 2017 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 828ACD1048E for ; Fri, 17 Mar 2017 10:01:42 +0000 (UTC) (envelope-from ralf.mardorf@rocketmail.com) Received: from nm13-vm7.bullet.mail.ir2.yahoo.com (nm13-vm7.bullet.mail.ir2.yahoo.com [212.82.96.186]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 00B9414B0 for ; Fri, 17 Mar 2017 10:01:41 +0000 (UTC) (envelope-from ralf.mardorf@rocketmail.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rocketmail.com; s=s2048; t=1489744893; bh=xV69McNzyzLBBdlJI9DWOjLQ6CL+yVWI5BZ3a+x+Ot0=; h=Date:From:To:Subject:In-Reply-To:References:From:Subject; b=pgz4R8JYs0zAT1eZ2l4ODmpsgfrQWazPEyU7pXjClfK/Wk417L4KD5fbH+vz1cLLFBoxmhvydBirkdxoyFO6ziYyk/T4feR9/iOkv5I0oemhPl20vAJ5yYjGRcl1dDUY5hs7rbfMvL7SBEDRRTi2eegfyXR9J5dLOli1lOnRvoZIW5AySIpO3bSbOFkdov/Lx37SgmQ7e8mEHEK85A3B3gehi7Se8XQSU2kKZI9Csexs/s6xP+qnj4zUPQDOL/fSBPxLriqgdj9TXhunvctES4oL2P0AEf4+ySaXdLDb4BqxhctqRqLKrPiXw2xqKqECDa9DRHRtacK2BKRh5i/rWA== Received: from [212.82.98.125] by nm13.bullet.mail.ir2.yahoo.com with NNFMP; 17 Mar 2017 10:01:33 -0000 Received: from [46.228.39.101] by tm18.bullet.mail.ir2.yahoo.com with NNFMP; 17 Mar 2017 10:01:33 -0000 Received: from [127.0.0.1] by smtp138.mail.ir2.yahoo.com with NNFMP; 17 Mar 2017 10:01:33 -0000 X-Yahoo-Newman-Id: 715875.29184.bm@smtp138.mail.ir2.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: PCErVv0VM1kwgjGJg.cF6U0UEcN.t57bZyJCToCtRf3Fiig _QkvW93Y5BCa_.wMXDTO65I9RAgi9IktHwQo1y1v9d1WPOY8TJD5fKtC6PwF eDAxMp0aY8b0s.YaO3tPZhCX4rlEnIVFh.4Nb8PBmZ.qWWpwQ2.0RsfsdO8J RigMraHo8BaHZlsY0keg_Z74EVw8d7DITFx6Ms5n.mlaevMVYhwg3bULF_B9 WT9caTRmPBcZWxFImJwBMtqRYBBx0U.KYgFgJg6R8zBAgrp1vWfo46dN.vhv w35EHqxjDc5uaVzN1l49M4vtCznfxLWMzj62oKZmkPm.u6Mnap94piWkoXGt zd8m4QiTJrMHHXZQ6twceoSutyFxKfiqm89TUS4mnfZki6M.pRwiUPx3MIN9 Mxj5o4IpNOBQBq4f7vArMGsHG5pgiJxZ0grYVdBmkocoePEHro6BQ5m3U4eo O8jhTUxsEbi0EupLyIrcpbrouLLTQ3QwxA.OQfpPhdfR4M5dXuxIoKpBnx7m AiwCvYciz_9pY4j.uYPFYt91kRo6NpbmfMAIqLUb341BjdGFfsePd75i_hVf U0HAYputVflr9AlaVQmmdVNKo7IwB0w-- X-Yahoo-SMTP: BeMCPs2swBABTJ3kAeEiC_hE0mz8jRexLddJfD8pI2j32fOacjBmXg-- Date: Fri, 17 Mar 2017 11:01:37 +0100 From: Ralf Mardorf To: freebsd-questions@freebsd.org Subject: Re: bootable ext. USB SSD for backup Message-ID: <20170317110137.51d1f849@archlinux.localdomain> In-Reply-To: <20170317100406.b8e3d390.freebsd@edvax.de> References: <20170316194612.GA1748@c720-r314251> <33953.128.135.52.6.1489694167.squirrel@cosmo.uchicago.edu> <92024f3c-2ab3-1741-97de-36455ca56b7e@gmx.net> <20170316213722.139560c8@archlinux.localdomain> <20170317100406.b8e3d390.freebsd@edvax.de> X-Mailer: Claws Mail 3.14.1-19-ge7206c0 (GTK+ 2.24.31; x86_64-arch-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 17 Mar 2017 10:01:42 -0000 On Fri, 17 Mar 2017 10:04:06 +0100, Polytropon wrote: >On Thu, 16 Mar 2017 21:37:22 +0100, Ralf Mardorf via freebsd-questions >wrote: >> On Thu, 16 Mar 2017 21:11:53 +0100, Martin S. Weber wrote: >> >Toshiba is clearly underselling the disk. >> >> I don't think so, I suspect that some bytes are reserved to >> compensate borked memory locations. > >Few years ago, I read that SSDs that are sold with size n are >actually produced as size 2 * n due to high failure rate during >production... I doubt this, since the chips are selected, before used for an SSD. OTOH the German Wiki mentions that a vendor should have used off-spec chips. However, my guess about borked memory cells is a half-truth, correct seems to be that "over provisioning" is used to provide workspace for the controller. One task of the controller seemingly is to handle borked memory cells, but it seems to be used as a buffer to avoid unneeded write cycles and to organize the available space, to avoid performance issues, if less space is free on a SSD. -- On Thu, 16 Mar 2017 23:32:14 -0600 (MDT), Warren Block wrote: >(The memory units used above are actually gwibblybytes (GwB), 1012 >7.9-bit bytes per kwibblybyte (KwB), 1011 KwB per mibblybyte (MwB), >and 1010 MwB per gwibblybyte, or about fourteen thousandths short of a >dwibblyliter (DwL).) "1 dwibblyliter" also named "1 Vogon" :p