From owner-freebsd-hardware@FreeBSD.ORG Fri Dec 30 06:01:16 2005 Return-Path: X-Original-To: freebsd-hardware@freebsd.org Delivered-To: freebsd-hardware@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 117F616A41F for ; Fri, 30 Dec 2005 06:01:16 +0000 (GMT) (envelope-from markir@paradise.net.nz) Received: from linda-5.paradise.net.nz (bm-5a.paradise.net.nz [203.96.152.184]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6858F43D58 for ; Fri, 30 Dec 2005 06:01:15 +0000 (GMT) (envelope-from markir@paradise.net.nz) Received: from smtp-3.paradise.net.nz (tclsnelb1-src-1.paradise.net.nz [203.96.152.172]) by linda-5.paradise.net.nz (Paradise.net.nz) with ESMTP id <0ISA005V4QRSW8@linda-5.paradise.net.nz> for freebsd-hardware@freebsd.org; Fri, 30 Dec 2005 18:47:54 +1300 (NZDT) Received: from [192.168.1.11] (218-101-29-175.dsl.clear.net.nz [218.101.29.175]) by smtp-3.paradise.net.nz (Postfix) with ESMTP id 831431251A6F; Fri, 30 Dec 2005 18:43:40 +1300 (NZDT) Date: Fri, 30 Dec 2005 18:43:37 +1300 From: Mark Kirkwood In-reply-to: <200512292136.50983.mlalvarez@manquehue.net> To: olivier@gautherot.net Message-id: <43B4C909.8020006@paradise.net.nz> MIME-version: 1.0 Content-type: text/plain; format=flowed; charset=ISO-8859-1 Content-transfer-encoding: 7bit X-Accept-Language: en-us, en User-Agent: Mozilla Thunderbird 1.0.6 (X11/20051106) References: <200512292134.jBTLYaSH001273@clunix.cl.msu.edu> <200512292136.50983.mlalvarez@manquehue.net> Cc: freebsd-hardware@freebsd.org Subject: Re: Harddrive size being reported incorrectly? X-BeenThere: freebsd-hardware@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: General discussion of FreeBSD hardware List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 30 Dec 2005 06:01:16 -0000 Olivier Gautherot wrote: > On Thursday 29 December 2005 18:34, Jerry McAllister wrote: > >>>>[...] >>>>When you slice and partition the drive, there will likely be a handful >>>>of sectors that don't round out to an even value so those are dropped. >>>>Then, when you do the newfs, some space is taken by the spare superblocks >>>>and finally the system reserves 8%. So, I would say you are getting >>>>it all. >>> >>>289GB is before the 8% reservation. I actually turned that off with tunefs. >> >>I strongly suggest you do not do that - at least completely off. >>Reduce it some, if you like, but keep some. > > > I too strongly recommend you keep these 8% in. > > The fact is that the space is not wasted: in the old days, it was meant > to prevent the system from happily creating files until it dies - beyond > 100%, files already opened could be written to but you could not create > new files. Some kind of "soft landing". I suppose it is still the case. > > Actually, a friend asked me a few weeks ago how the file system could > reach 110% and he was speculating on how the system could use the > swap partition to get to this level: it was not the swap partition but this > extra space artificially held up. > > You can safely and without afterthoughts let this 8% in. > In addition, there are some potentially undesirable side effects that result from reduction - from the tunefs manpage discussing minfree: Note that lowering the threshold can adversely affect performance: o Settings of 5% and less force space optimization to always be used which will greatly increase the overhead for file writes. o The file system's ability to avoid fragmentation will be reduced when the total free space, including the reserve, drops below 15%. As free space approaches zero, throughput can degrade by up to a factor of three over the performance obtained at a 10% threshold. The first effect can be mitigated by specifying '-o time', but I always leave it at the 8% default (fewer customizations for me to forget...). Cheers Mark