From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx2.redhat.com (mx2.redhat.com [10.255.15.25]) by int-mx2.corp.redhat.com (8.13.1/8.13.1) with ESMTP id l51Jbwea002522 for ; Fri, 1 Jun 2007 15:37:58 -0400 Received: from bycast.com (bycast.com [209.139.229.1]) by mx2.redhat.com (8.13.1/8.13.1) with ESMTP id l51JbqOx011544 for ; Fri, 1 Jun 2007 15:37:53 -0400 Received: from [192.168.110.200] (account kjamieson HELO [192.168.110.200]) by bycast.com (CommuniGate Pro SMTP 4.3.9) with ESMTPA id 1916926 for linux-lvm@redhat.com; Fri, 01 Jun 2007 12:37:47 -0700 Message-ID: <4660758B.7010908@bycast.com> Date: Fri, 01 Jun 2007 12:37:47 -0700 From: Kevin Jamieson MIME-Version: 1.0 Subject: Re: [linux-lvm] Should I expect snapshot origin LV's to be 10x slower? Content-Transfer-Encoding: 7bit Reply-To: kjamieson@bycast.com, LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: linux-lvm@redhat.com Alex Owen wrote: > I have been using commands of the form: > time dd if=/dev/zero of=/dev/volgroup/test bs=1M count=100 > to get speeds for copying to a LVM device both WITH and WITHOUT a > single snapshot. > > It seems that writes take >=10 times longer the first time a newly > snapshot origin device is written to. You may want to try the kernel patch posted here: http://marc.info/?l=dm-devel&m=118056593528910&w=1 That change gave me a significant speedup in similar tests. Kevin