From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peri Hankey Subject: Re: A snapshot is not (really) a cow Date: Sun, 26 Sep 2004 22:29:18 +0100 Sender: xen-devel-admin@lists.sourceforge.net Message-ID: <415734AE.5090907@thegreen.co.uk> References: Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------050907000400070609090909" Return-path: In-Reply-To: Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: Ian Pratt Cc: Christian Limpach , xen-devel@lists.sourceforge.net List-Id: xen-devel@lists.xenproject.org This is a multi-part message in MIME format. --------------050907000400070609090909 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit I'm not aware of anything that is trying to use NBD - I did experiment a bit a while back, but didn't get anywhere. I thought xen might be using it behind the scenes in some way. I have attached some tar-zipped output which may help. lvm2-nbd-problem-20040916/ lvm2-nbd-problem-20040916/messages-log # messages during vchange -ay lvm2-nbd-problem-20040916/services-list # services that were enabled lvm2-nbd-problem-20040916/syslog-start # syslog start at reboot lvm2-nbd-problem-20040916/mem-slab-1 # before vchange -ay lvm2-nbd-problem-20040916/mem-slab-2 # after vchange -ay lvm2-nbd-problem-20040916/vgchange-ay-result # response to command lvm2-nbd-problem-20040916/cmdline # xen0 kernel command line xen version date: xen-2.0-20040924. I am puzzled that in /var/log/messages it almost immediately starts trying to access nbd devices - none are listed as existing in /dev. Also I'm not sure what the '[' relates to. There is a note about the symbols matching 2.6.8, but I am running 2.6.8.1. Also it says kernel modules ere not enabled, but lsmod shows: ... # lsmod Module Size Used by nfsd 91720 8 exportfs 5248 1 nfsd Should I be doing anything about kernel symbols? I build and install straight out of the box with no special config: make world (as orndinary user) make install (as root) Too late. I hope this helps. Thanks Peri >>I successfully created 2 new snapshots while another was in use as the >>root file system of a xenU domain. Previously this had failed >>immediately. Then the next lvcreate -s failed with a message about >>running out of memory, as before. >> >>I wonder whether the timing problem I have which affects rpm is also >>causing some problem? >> >>The relevant bit of /var/log/messages is: >> >>... lots of nbdNNN messages ... >> >> > >Are you using NBD? Our default kernel has it compiled in, but it >looks like some of your start up scripts are trying to initialise >it, or you have some daemon that's polling the devices. > >It looks like the error messages are hammering the machine pretty >hard from time to time. It's definitely worth figuring out what's >causing it. Or, compile nbd out of the kernel... > > > >>Sep 26 19:53:44 a4 kernel: lvcreate: page allocation failure. order:0, >>mode:0xd0 >>Sep 26 19:53:44 a4 kernel: [__alloc_pages+824/842] >> >> > >Seeing the output of /proc/slabinfo and /proc/meminfo might be >interesting. And idea why the machine might be under memory pressure? > >Ian > > >------------------------------------------------------- >This SF.Net email is sponsored by: YOU BE THE JUDGE. Be one of 170 >Project Admins to receive an Apple iPod Mini FREE for your judgement on >who ports your project to Linux PPC the best. Sponsored by IBM. >Deadline: Sept. 24. Go here: http://sf.net/ppc_contest.php >_______________________________________________ >Xen-devel mailing list >Xen-devel@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/xen-devel > > > > --------------050907000400070609090909 Content-Type: application/x-gzip; name="lvm2-nbd-problem-20040916-tar.gz" Content-Transfer-Encoding: base64 Content-Disposition: inline; filename="lvm2-nbd-problem-20040916-tar.gz" H4sIAKQzV0EAA+1d64/jNpKfz/1XEJsPyWLisUjqaSSNzc7icAE2t4ubvbsPwcCgJdpWrIdH kt3d+euPL+tt2ZLs7mwiDjBli2L9WGSxWHxUOziGaBatvNk+iVcBDWdI03TNgeb83c0S52gZ BqMi1an4DDWIDBNDE+rvNIgNHb4Dxu2qcD4d0owkALxL4jjreu9S/r9pCs72f0jTlGxoOgvi zTgMDWqaqetn+p91dt7/yDJE/5uagd4B7TYidqc/eP9/onuATIDQQsMLaAGigx1NIhosAI28 ZUK/HGiaLcCP838AmiRx8i3w6BEwjYHI/Bak1M3iBGgPHXzEu9YC/LfkBZ62NAJRnM0SSryX rpIXa2BdV4Pjxt2SaEMXYM80GpAgiF2S+XEE1sQPDgn9AOLEo8lC+xaEsUcX2rPXyRD8vFwK LkvOMH1vI31u6+gzqD7WnjG25+x/nXRz+85lw4BAc/04jEU3911Iw6VL3C2VrN/bzpwNyc+g 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