From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailsrv.cs.umass.edu (mailsrv.cs.umass.edu [128.119.240.136]) by sourceware.org (Postfix) with ESMTPS id 1FB773858C20 for ; Mon, 31 Jan 2022 14:59:19 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 1FB773858C20 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=cs.umass.edu Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=cs.umass.edu Received: from [192.168.50.218] (c-24-62-201-179.hsd1.ma.comcast.net [24.62.201.179]) by mailsrv.cs.umass.edu (Postfix) with ESMTPSA id 41C314023BB9; Mon, 31 Jan 2022 09:59:18 -0500 (EST) Reply-To: moss@cs.umass.edu Subject: Re: Renaming (with 'mv') very large files is SLOW To: cygwin@kosowsky.org, cygwin@cygwin.com References: <25079.63376.349893.86395@consult.pretender> From: Eliot Moss Message-ID: Date: Mon, 31 Jan 2022 09:59:17 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <25079.63376.349893.86395@consult.pretender> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.2 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS, NICE_REPLY_A, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: cygwin@cygwin.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: General Cygwin discussions and problem reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 31 Jan 2022 14:59:21 -0000 On 1/31/2022 9:52 AM, cygwin@kosowsky.org wrote: > I tried renaming some very large files (20-40 GB) using: > mv > without changing the directory of course. > > The process took about 10-20 minutes with Task Manager showing disk > activity of 100+ MB/s. > > Is there something about such large 'renaming' that actually results > in the file being really moved (aka copied) rather than just renamed? The two places are probably on different volumes (loosely, different disks). That requires a physical move, even under Linux. Your volumes seem a bit slow to access - is one perhaps across a slow network? The rates you cite suggest movement of 50Mb/s (50Mb read + 50Mb write = 100Mb overall). For 40 Gb that should take 40Gb / 50Mb = about 820 secs = a little under 14 mins. (When I say your volumes are slow, I speak from the luxury of having a 2Tb solid state drive! Actually, those speeds may be reasonable depending on the nature of your system.) If the two locations are on different drives, there's no real avoiding this. Regards - Eliot Moss