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[libvirt-users] KVM virtio bonding bandwidth problem
by Didier Moens 22 Jan '10

22 Jan '10

(first post) Dear all, I have been wrestling with this issue for the past few days ; googling around doesn't seem to yield anything useful, hence this cry for help. Setup : - I am running several RHEL5.4 KVM virtio guest instances on a Dell PE R805 RHEL5.4 host. Host and guests are fully updated ; I am using iperf to test available bandwidth from 3 different locations (clients) in the network to both the host and the guests . - To increase both bandwidth and fail-over, 3 1Gb network interfaces (BCM5708, bnx2 driver) on the host are bonded (802.3ad) to a 3 Gb/s bond0, which is bridged. As all guest interfaces are connected to the bridge, I would expect total available bandwidth to all guests to be in the range of 2-2.5 Gb/s. - Testing with one external client connection to the bare metal host yields approx. 940 Mb/s ; - Testing with 3 simultaneous connections to the host yields 2.5 Gb/s, which confirms a successful bonding setup. Problem : Unfortunately, available bandwidth to the guests proves to be problematic : 1. One client to one guest : 250-600 Mb/s ; 2a. One client to 3 guests : 300-350 Mb/s to each guest, total not exceeding 980 Mb/s; 2b. Three clients to 3 guests : 300-350 Mb/s to each guest ; 2c. Three clients to host and 2 guests : 940 Mb/s (host) + 500 Mb/s to each guest. Conclusions : 1. I am experiencing a 40% performance hit (600 Mb/s) on each individual virtio guest connection ; 2. Total simultaneous bandwidth to all guests seems to be capped at 1 Gb/s ; quite problematic, as this renders my server consolidation almost useless. I could bridge each host network interface separately and assign guest interfaces by hand, but that would defy the whole idea of load balancing and failover which is provided by the host bonding. Any ideas anyone, or am I peeking in the wrong direction (clueless setup, flawed testing methodology, ...) ? Thanks in advance for any help, Didier -- Didier Moens , IT services Department for Molecular Biomedical Research (DMBR) VIB - Ghent University

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[libvirt-users] libvirt restarting vms on restart?
by Tom Hughes 19 Jan '10

19 Jan '10

Recent versions of libvirt seem to have taken to starting new copies of my vms when they restart. Any vm marked to start when libvirt is started is started, even if it is already running, which leads to multiple running vms trying to use the same disk image. I think this probably started with the upgrade from 0.7.4 to 0.7.5 but I can't be entirely sure as I only realised yesterday that I had somehow managed to get multiple instances of a VM running. It definitely happened this morning when the updated from 0.7.5.-1 to 0.7.5-3 in the F12 virt-preview repo caused a restart. Tom -- Tom Hughes (tom(a)compton.nu) http://www.compton.nu/

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Re: [libvirt-users] [libvirt] Set MAC address for host virtual interface?
by Neil Aggarwal 16 Jan '10

16 Jan '10

Daniel: This discussion used to be on the libvirt list, but seems more appropriate for the users list so I am replying here. > At some time in the past we did set the MAC address on the > host interface > too, but it caused networking problems in some configurations I see. Thanks for the background info. > I guess you have Cacti configured to pull stats directly from the TAP > devices on the host ? I am using bridging, but you are correct. I installed snmpd and have Cacti pulling stats from it. > Cacti has the ability to run scripts to pull > in statistics, so my recommendation would be to add a shell script which > calls the 'domifstat' command in virsh > virsh domifstat DOMNAME TAPDEVNAME The Cacti server is running in a separate machine, not on the host. I guess I will have to find something that makes the domifstat data available via an snmp interface. Do you know of such a tool? Thanks, Neil -- Neil Aggarwal, (281)846-8957, http://UnmeteredVPS.net/centos CentOS 5.4 VPS with unmetered bandwidth only $25/month! No overage charges, 7 day free trial, PayPal, Google Checkout

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[libvirt-users] Testing 123...
by Daniel P. Berrange 15 Jan '10

15 Jan '10

...456 Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|

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