From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Dilger Subject: Re: common layout xattr Date: Wed, 15 Jul 2009 18:05:14 -0400 Message-ID: <20090715220514.GJ14175@webber.adilger.int> References: <1247693090-27796-9-git-send-email-sage@newdream.net> <1247693090-27796-10-git-send-email-sage@newdream.net> <1247693090-27796-11-git-send-email-sage@newdream.net> <1247693090-27796-12-git-send-email-sage@newdream.net> <1247693090-27796-13-git-send-email-sage@newdream.net> <1247693090-27796-14-git-send-email-sage@newdream.net> <1247693090-27796-15-git-send-email-sage@newdream.net> <1247693090-27796-16-git-send-email-sage@newdream.net> <1247693090-27796-17-git-send-email-sage@newdream.net> <1247693090-27796-18-git-send-email-sage@newdream.net> Mime-Version: 1.0 Content-Type: text/plain; CHARSET=US-ASCII Content-Transfer-Encoding: 7BIT Cc: linux-fsdevel@vger.kernel.org To: Sage Weil Return-path: Received: from sca-es-mail-2.Sun.COM ([192.18.43.133]:45126 "EHLO sca-es-mail-2.sun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752749AbZGOWFW (ORCPT ); Wed, 15 Jul 2009 18:05:22 -0400 Received: from fe-sfbay-10.sun.com ([192.18.43.129]) by sca-es-mail-2.sun.com (8.13.7+Sun/8.12.9) with ESMTP id n6FM5IeP017818 for ; Wed, 15 Jul 2009 15:05:18 -0700 (PDT) Content-disposition: inline Received: from conversion-daemon.fe-sfbay-10.sun.com by fe-sfbay-10.sun.com (Sun Java(tm) System Messaging Server 7u2-7.02 64bit (built Apr 16 2009)) id <0KMU00500F9CQ600@fe-sfbay-10.sun.com> for linux-fsdevel@vger.kernel.org; Wed, 15 Jul 2009 15:05:18 -0700 (PDT) In-reply-to: <1247693090-27796-18-git-send-email-sage@newdream.net> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Jul 15, 2009 14:24 -0700, Sage Weil wrote: > A few Ceph ioctls for getting and setting file layout (striping) > parameters. > + > +#define CEPH_IOC_GET_LAYOUT _IOR(CEPH_IOCTL_MAGIC, 1, struct ceph_file_layout) > +#define CEPH_IOC_SET_LAYOUT _IOW(CEPH_IOCTL_MAGIC, 2, struct ceph_file_layout) I've been trying to get some steam behind a more common interface for backing up and restoring file layout information, using virtual xattrs. This will allow tar/rsync/etc to back up the layout xattr and then restore it (preferrably before the data is written) to the target, so that any user-specified file layout is preserved. I'm thinking of using simple ASCII key=value pairs to store basic layout information like chunk size, stripe count, mirror count, RAID type, etc. Some of them may not be applicable/usable by all filesystems, but having a handful of "well known" keys and values for a common xattr name would at least be better than what we have now (which is nothing). Something like (not necessarily a firm proposal yet): trusted.common_layout: chunk_bytes=65536 stripe_count=32 mirror_count=3 raid_type=1+0 Is this something you would be interested to pursue? I've also discussed this with Panasas, and they had some interest in this as well. Any GPFS developers watching? Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc.