Zhao, Yunfeng
2006-Jul-20 10:15 UTC
RE: [Xen-users] Error: Device 769 (vbd) could not be connected...Limit of 25 domains.
This is a known issue. It has been fixed in xen unstable. The problem is loop device is not leased after the guest destroyed. If execute "losetup -d /dev/loopX" in domain0, the problem will be solved temporarily.>-----Original Message----- >From: xen-users-bounces@lists.xensource.com >[mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Thomas Karsten >Sent: 2006年7月20日 17:26 >To: xen-users@lists.xensource.com >Subject: Re: [Xen-users] Error: Device 769 (vbd) could not be connected...Limit >of 25 domains. > >Hi, > >I used the Debian GNU/Linux Etch system on the Xen 3.0 Live CD (Version >1.0) to have a look where I am doing some mistake in my system''s >configuration. I used the standard config file ''/root/deb-conf'' and >launched the following command: > ># for ((i=100; i < 140; i++)); do xm create /root/deb-conf >name=guestdom$i; done > >This time I was able to create up to 15 guest domains, all the others >resulted in the following error message: > >Device 2049 (vbd) could not be connected. Backend device not found. > >(As far as I experienced, the device 2049 is /dev/sda1.) > >However, I would like to know, if some of you also run into this problem, >when launching this command on the same system (Xen 3.0 Live CD). I >tested this on another machine, where I could only create up to 7 >concurrent guest domains. > >Is the problem that I face related to the hardware? Or is it only related >to the software (i.e. configuration of the whole system)? In latter case, >why does the Live CD behave different on different computers? Or am I >missing an important point in the configuration process? > >I am very curious about this problem and how to solve it, since it has >been a topic on this mailing list many times, but I did not see any >solution posted. > >I hope somebody can try to launch this command using that Xen Live CD and >tell me about the results. > >Thank you very much, >Thomas > >On Wednesday 19 July 2006 18:18, Thomas Karsten wrote: >> Hello, >> >> I am running Xen 3.0.2 in an Ubuntu 6.06 Linux system (kernel >> 2.6.16-xen). Xend is running and works well. >> >> I would like to use Xen to run about 80 domains (for testing purpose). >> All domains share the same image file (which therefor is mounted >> ''readonly'' by Xen) and each domain is configured to use only 10 MB of >> RAM. I am using a script to generate name, hostname and IP address for >> each guest (it simply loops over i and calls:''xm create name=guestdom$i >> hostname=$i ip=192.168.1. $i''). >> >> Everything works fine, but after 25 concurrent running domains Xen >> refuses to create any further domains, giving me the error: >> >> Error: Device 769 (vbd) could not be connected. Hotplug scripts not >> working. >> >> On this mailing list I found several threads dealing with this error >> message. However, I did not find that anybody is facing this kind of >> limitation that I have. For your information, the number of loopback >> devices in my system is 132. Also, I am not running out of memory, this >> would be stated by Xen (I have 1500 MB of RAM, where 500 MB are >> occupied by Xen). >> >> I can remove a guest domain and create a new one, this is no problem. >> However, on my system I am not able to create more than 25 domains at >> the same time. Can anybody help please? >> >> Thank you very much, all ideas are appreciated, >> Thomas > >_______________________________________________ >Xen-users mailing list >Xen-users@lists.xensource.com >http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Thomas Karsten
2006-Jul-28 01:58 UTC
Re: [Xen-users] Error: Device 769 (vbd) could not be connected...Limit of 25 domains. SOLVED.
Hallo, thanks for your suggestion. On Thursday 20 July 2006 18:15, you wrote:> This is a known issue. > It has been fixed in xen unstable. > The problem is loop device is not leased after the guest destroyed. > If execute "losetup -d /dev/loopX" in domain0, the problem will be solved temporarily.Since I have 255 loopback devices installed in my system, I am not running out of loopback devices (because this limitation also occures when starting the domUs for the first time). However, after some testing I manage the handling of the loopback devices on my own now and pass each loopback device (physical device) to Xen rather than the image file (file backed vbd): for ((i=10; i < 130; i++)); do loop_device=$(losetup -f) losetup $loop_device /xen-images/guestdom1.img xm create /etc/xen/guestdoms \ name="guestdom$i" \ dev="phy:$loop_device,sda1,ro" done This works well and it does not end up in the error message. Of course, I also have to take care of detaching the image from each loopback device after the guest shut down. Using this method I am able to create up to 111 concurrent running domUs, afterwards I get the error message "Error: (12, ''Cannot allocate memory'')". This is a known limitation caused by Xen''s internal heap of 16 MB (http://lists.xensource.com/archives/html/xen-devel/2006-04/msg00321.html). I just wonder, why I get a problem using the file backed vbds, but why I don''t run into this problem using the physical device. I thought that Xen internally also attaches the image file to a free loopback device. If this was the case, then why can Xen create so many domUs when physical devices are passed to it, but has a problem with using file backed vbd? Any ideas for this? By the way, I also found out that Xen will create a guest faster when passing the physical device to it than just passing the image file. Thanks, Thomas> >On Wednesday 19 July 2006 18:18, Thomas Karsten wrote: > >> Hello, > >> > >> I am running Xen 3.0.2 in an Ubuntu 6.06 Linux system (kernel > >> 2.6.16-xen). Xend is running and works well. > >> > >> I would like to use Xen to run about 80 domains (for testing purpose). > >> All domains share the same image file (which therefor is mounted > >> ''readonly'' by Xen) and each domain is configured to use only 10 MB of > >> RAM. I am using a script to generate name, hostname and IP address for > >> each guest (it simply loops over i and calls:''xm create name=guestdom$i > >> hostname=$i ip=192.168.1. $i''). > >> > >> Everything works fine, but after 25 concurrent running domains Xen > >> refuses to create any further domains, giving me the error: > >> > >> Error: Device 769 (vbd) could not be connected. Hotplug scripts not > >> working. > >> > >> On this mailing list I found several threads dealing with this error > >> message. However, I did not find that anybody is facing this kind of > >> limitation that I have. For your information, the number of loopback > >> devices in my system is 132. Also, I am not running out of memory, this > >> would be stated by Xen (I have 1500 MB of RAM, where 500 MB are > >> occupied by Xen). > >> > >> I can remove a guest domain and create a new one, this is no problem. > >> However, on my system I am not able to create more than 25 domains at > >> the same time. Can anybody help please? > >> > >> Thank you very much, all ideas are appreciated, > >> Thomas > > > >_______________________________________________ > >Xen-users mailing list > >Xen-users@lists.xensource.com > >http://lists.xensource.com/xen-users >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users