From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Fri, 06 Jun 2008 11:32:31 -0700 (PDT) Received: from cuda.sgi.com ([192.48.176.15]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m56IWQWF025675 for ; Fri, 6 Jun 2008 11:32:26 -0700 Received: from defout.telus.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 378D417921B4 for ; Fri, 6 Jun 2008 11:33:19 -0700 (PDT) Received: from defout.telus.net (defout.telus.net [199.185.220.240]) by cuda.sgi.com with ESMTP id KuLPhha9m071OQmF for ; Fri, 06 Jun 2008 11:33:19 -0700 (PDT) Received: from priv-edtnaa04.telusplanet.net ([216.232.71.140]) by priv-edtnes25.telusplanet.net (InterMail vM.7.08.02.02 201-2186-121-104-20070414) with ESMTP id <20080606183258.QPM16573.priv-edtnes25.telusplanet.net@priv-edtnaa04.telusplanet.net> for ; Fri, 6 Jun 2008 12:32:58 -0600 Received: from mail.zymeworks.com (s216-232-71-140.bc.hsia.telus.net [216.232.71.140]) by priv-edtnaa04.telusplanet.net (BorderWare MXtreme Infinity Mail Firewall) with ESMTP id D3G198CHK8 for ; Fri, 6 Jun 2008 12:33:18 -0600 (MDT) Received: from localhost (localhost [127.0.0.1]) by mail.zymeworks.com (Postfix) with ESMTP id 4FD60756D2D for ; Fri, 6 Jun 2008 11:33:18 -0700 (PDT) Received: from mail.zymeworks.com ([127.0.0.1]) by localhost (barista.lan.zymeworks.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id elqEHuWEccG6 for ; Fri, 6 Jun 2008 11:33:17 -0700 (PDT) Received: from zubrowka.lan.zymeworks.com (zubrowka.lan.zymeworks.com [10.3.3.16]) by mail.zymeworks.com (Postfix) with ESMTP id DC29D756D22 for ; Fri, 6 Jun 2008 11:33:17 -0700 (PDT) Message-Id: From: Kamil Kisiel Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (Apple Message framework v919.2) Subject: XFS and block-level snapshots Date: Fri, 6 Jun 2008 11:33:17 -0700 Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: xfs@oss.sgi.com Hello, I had a question about XFS integrity and performing block-level snapshots. We currently have a 2TB (but growing soon..) volume mounted by a Linux host with kernel 2.6.23 over iSCSI from our SAN. Our SAN unit has the capability to perform block-level snapshots, which is done at regular intervals. I know that it is recommended to perform an xfs_freeze before performing a snapshot. However, the control of the snapshots is independent from the OS, which currently has no knowledge of their occurrence. I'm curious as to the repercussions of this. I understand that in all likelyhood, the integrity of files which are currently being written will not be preserved. However, even with an xfs_freeze this is not guaranteed, as an application may require additional disk transactions to maintain the file in a valid state (it is not necessarily atomic, depending on the application). As far as metadata transactions are concerned, the journal should make these atomic, so there should not be any problem there? Basically, I'd like to know what is the worst that could happen, and why an xfs_freeze is necessary in this scenario. ____________ Kamil Kisiel HPC Systems Engineer, Zymeworks Inc. 201-1401 West Broadway, Vancouver, BC, V6H 1H6, Canada Tel: (604) 678-1388 ext. 135 Fax: (604) 737-7077 www.zymeworks.com