From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steve French Subject: Re: copy-on-write files Date: Mon, 11 May 2009 13:25:23 -0500 Message-ID: <524f69650905111125n23c5624fh27b4612e1076e3ca@mail.gmail.com> References: <524f69650905111008p4b3d9256qdd0a86c08db31b37@mail.gmail.com> <20090511175327.GA30293@mail.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE To: Steve French , samba-technical , linux-fsdevel Return-path: Received: from mail-gx0-f166.google.com ([209.85.217.166]:57163 "EHLO mail-gx0-f166.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757957AbZEKSZX convert rfc822-to-8bit (ORCPT ); Mon, 11 May 2009 14:25:23 -0400 Received: by gxk10 with SMTP id 10so2896863gxk.13 for ; Mon, 11 May 2009 11:25:23 -0700 (PDT) In-Reply-To: <20090511175327.GA30293@mail.oracle.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, May 11, 2009 at 12:53 PM, Joel Becker = wrote: > On Mon, May 11, 2009 at 12:08:17PM -0500, Steve French wrote: >> Joel, >> Looking at your documentation for the new "reflink" syscall (to crea= te >> copy-on-write files): >> http://git.kernel.org/?p=3Dlinux/kernel/git/jlbec/ocfs2.git;a=3Dblob= ;f=3DDocumentation/filesystems/reflink.txt;h=3D58a6b3879114c0cb591fb736= 152b30291037edd2;hb=3Dc04db1c934e67337318b177688c0b882297fdd66 >> >> Have you looked at whether this is close enough to the existing (e.g= =2E >> Windows NTFS) copy-on-write syntax/feature so that we could use it >> under Samba (and on the client side from cifs and in the future smb2= ). >> =A0 Windows added copy-on-write about 9 or 10 years ago and uses it >> extensively. although I have not researched enough to see what >> creating these would look like over the network. > > =A0 =A0 =A0 =A0I didn't know NTFS had it There are lots of references to the various services that use copy on w= rite (e.g. the "Groveler" service, which I first noticed back in Windows 200= 0 copy-on-write linking remote windows install images, which can be quite= big, apparently saving enormous amounts of disk space, and also the "SIS" or "Single Instance Store" service which is an optional component of Windo= ws servers, and I saw a reference to Vista using the same NTFS copy-on-write feature for some form of backup/snapshot) but this would be a better question for a Windows programmer not a Linux kernel developer :) copy-on-write links seem to be represented as "reparse points" (a type = of Windows inode) with a tag "IO_REPARSE_TAG_SIS" (to distinguish it from other special purpose inodes such as symlinks, DFS referrals and j= unctions) http://msdn.microsoft.com/en-us/library/aa365511(VS.85).aspx Apparently they can be sent over the network based on section 2.4.35 of http://msdn.microsoft.com/en-us/library/cc232086(PROT.13).aspx --=20 Thanks, Steve -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html