From nobody Thu Jan 13 08:45:33 2022 X-Original-To: questions@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 6A97A19574D2 for ; Thu, 13 Jan 2022 08:45:45 +0000 (UTC) (envelope-from 4250.82.1d4d90000842c91.9e6aa9812e66f269b023011dad26e622@email-od.com) Received: from s1-b0c6.socketlabs.email-od.com (s1-b0c6.socketlabs.email-od.com [142.0.176.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4JZJ143kSrz3mdm for ; Thu, 13 Jan 2022 08:45:44 +0000 (UTC) (envelope-from 4250.82.1d4d90000842c91.9e6aa9812e66f269b023011dad26e622@email-od.com) DKIM-Signature: v=1; a=rsa-sha256; d=email-od.com;i=@email-od.com;s=dkim; c=relaxed/relaxed; q=dns/txt; t=1642063545; x=1644655545; h=content-transfer-encoding:content-type:mime-version:references:in-reply-to:message-id:subject:cc:to:from:date:x-thread-info; bh=BLLo0ixftwRlQo6oHpEwSAVDqovKbaNwhkKO/Aj9824=; b=Dg6UyALl4325eQvkAOi42SO+KAgwYBRcTHQK3/f9JgmVL3q3wqOSB2KRugqyQn4/Nadyk8bqhpDCCrm4vL+2hiKyDIDoT35wgxnHjCfISW5Se+P8vOGvoJx0JVqAd25HPaPZn+OegGMOSv9DZ4cXHKTOkbxiDNUOOhfm5qi+llw= X-Thread-Info: NDI1MC4xMi4xZDRkOTAwMDA4NDJjOTEucXVlc3Rpb25zPWZyZWVic2Qub3Jn Received: from r1.us-east-1.aws.in.socketlabs.com (r1.us-east-1.aws.in.socketlabs.com [142.0.191.1]) by mxsg2.email-od.com with ESMTP(version=Tls12 cipher=Aes256 bits=256); Thu, 13 Jan 2022 03:45:35 -0500 Received: from smtp.lan.sohara.org (EMTPY [185.202.17.215]) by r1.us-east-1.aws.in.socketlabs.com with ESMTP(version=Tls12 cipher=Aes256 bits=256); Thu, 13 Jan 2022 03:45:34 -0500 Received: from [192.168.63.1] (helo=steve.lan.sohara.org) by smtp.lan.sohara.org with smtp (Exim 4.94.2 (FreeBSD)) (envelope-from ) id 1n7vjh-000B9j-8s; Thu, 13 Jan 2022 08:45:33 +0000 Date: Thu, 13 Jan 2022 08:45:33 +0000 From: Steve O'Hara-Smith To: Roderick Cc: FreeBSD Questions List Subject: Re: dd and mbr Message-Id: <20220113084533.6f59428cf802930c62e61230@sohara.org> In-Reply-To: <5ad46ace-9241-bbba-df61-162b3ffe461b@gmail.com> References: <4af920fc-eff1-a92e-d36e-1ba97079864c@gmail.com> <20220112010402.GG61872@eureka.lemis.com> <20220112214107.GI61872@eureka.lemis.com> <5ad46ace-9241-bbba-df61-162b3ffe461b@gmail.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; amd64-portbld-freebsd13.0) X-Clacks-Overhead: "GNU Terry Pratchett" List-Id: User questions List-Archive: https://lists.freebsd.org/archives/freebsd-questions List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-questions@freebsd.org X-BeenThere: freebsd-questions@freebsd.org Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4JZJ143kSrz3mdm X-Spamd-Bar: / Authentication-Results: mx1.freebsd.org; dkim=pass header.d=email-od.com header.s=dkim header.b=Dg6UyALl; dmarc=none; spf=pass (mx1.freebsd.org: domain of 4250.82.1d4d90000842c91.9e6aa9812e66f269b023011dad26e622@email-od.com designates 142.0.176.198 as permitted sender) smtp.mailfrom=4250.82.1d4d90000842c91.9e6aa9812e66f269b023011dad26e622@email-od.com X-Spamd-Result: default: False [-0.40 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.70)[-0.698]; R_DKIM_ALLOW(-0.20)[email-od.com:s=dkim]; FROM_HAS_DN(0.00)[]; MV_CASE(0.50)[]; R_SPF_ALLOW(-0.20)[+ip4:142.0.176.0/20]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[sohara.org]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_SPAM_SHORT(1.00)[1.000]; RCVD_COUNT_THREE(0.00)[4]; TO_MATCH_ENVRCPT_SOME(0.00)[]; TO_DN_ALL(0.00)[]; DKIM_TRACE(0.00)[email-od.com:+]; RCPT_COUNT_TWO(0.00)[2]; RCVD_IN_DNSWL_NONE(0.00)[142.0.191.1:received]; RWL_MAILSPIKE_EXCELLENT(0.00)[142.0.176.198:from]; FREEMAIL_TO(0.00)[gmail.com]; FORGED_SENDER(0.30)[steve@sohara.org,4250.82.1d4d90000842c91.9e6aa9812e66f269b023011dad26e622@email-od.com]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_LAST(0.00)[]; ASN(0.00)[asn:7381, ipnet:142.0.176.0/22, country:US]; FROM_NEQ_ENVFROM(0.00)[steve@sohara.org,4250.82.1d4d90000842c91.9e6aa9812e66f269b023011dad26e622@email-od.com]; MID_RHS_MATCH_FROM(0.00)[]; DWL_DNSWL_NONE(0.00)[email-od.com:dkim] X-ThisMailContainsUnwantedMimeParts: N On Thu, 13 Jan 2022 08:32:26 +0000 (UTC) Roderick wrote: > > On Thu, 13 Jan 2022, Greg 'groggy' Lehey wrote: > > > As others have suggested, use bs=64k. Otherwise dd does an IO for > > every single sector. The speedup is really in the order of 100x. > > I used bs=1m. I hope that was also OK. In any case faster than without it. That's always been fine when I've used it and you can be sure that it's bigger than any physical write size - but at 64k I think it's as fast as it's going to get. -- Steve O'Hara-Smith