From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: Re: [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM Date: Sun, 25 Oct 2009 11:55:32 +0100 Message-ID: <4AE42EA4.5080009@wpkg.org> References: <4ADE988B.2070303@lab.ntt.co.jp> <4AE07A7F.8000002@redhat.com> <8fd1d76d0910230341w7978ac09te203ef34b79a86c6@mail.gmail.com> <90eb1dc70910230714h65e918a4n255bcf97634b26b0@mail.gmail.com> <20091023145815.GE18955@arachsys.com> <4AE1E25C.9010404@wpkg.org> <90D306BE6EBC8D428A824FBBA7A3113D012F07D53B@ronja.maurer-it.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Chris Webb , Javier Guerra , MORITA Kazutaka , "linux-fsdevel@vger.kernel.org" , Avi Kivity , "kvm@vger.kernel.org" , "qemu-devel@nongnu.org" To: Dietmar Maurer Return-path: Received: from mx03.syneticon.net ([78.111.66.105]:53741 "EHLO mx03.syneticon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753273AbZJYKza (ORCPT ); Sun, 25 Oct 2009 06:55:30 -0400 In-Reply-To: <90D306BE6EBC8D428A824FBBA7A3113D012F07D53B@ronja.maurer-it.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Dietmar Maurer wrote: >> Also, on _loaded_ systems, I noticed creating/removing logical volumes >> can take really long (several minutes); where allocating a file of a >> given size would just take a fraction of that. > > Allocating a file takes much longer, unless you use a 'sparse' file. If you mean "allocating" like with: dd if=/dev/zero of=image bs=1G count=50 Then of course, that's a lot of IO. As you mentioned, you can create a sparse file (but then, you'll end up with a lot of fragmentation). But a better way would be to use persistent preallocation (fallocate), instead of "traditional" dd or a sparse file. -- Tomasz Chmielewski http://wpkg.org