Hi!
In our cluster system (16 nodes, each node 32GB RAM and two quad-core
CPUs) we are using Gentoo with kvm 0.15.0 for executing virtual
machines.
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Linux asok01 3.0.4-gentoo #1 SMP Thu Sep 8 09:15:01 CEST 2011 x86_64
Intel(R) Xeon(R) CPU X5355 @ 2.66GHz GenuineIntel GNU/Linux
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Migrating VMs between server nodes works perfectly fine, except for
migrating large memory VMs to local disk (a.k.a. suspending the VM).
The command we use for migrating (suspending) the VM is:
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QEMU 0.15.0 monitor - type 'help' for more information
(qemu) migrate -d "exec:gzip -c > /var/run/kvm/suspend-vm-219.bin.gz"
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For most VMs, this command triggers the suspension procedure, having
the file suspend-vm-219.bin.gz being generated. The progress can be
monitored using:
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QEMU 0.15.0 monitor - type 'help' for more information
(qemu) info migrate
Migration status: active
transferred ram: 36758 kbytes
remaining ram: 4164888 kbytes
total ram: 4211136 kbytes
(qemu)
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After some seconds, the memory of this VM has been written to disk,
which concludes the migration process:
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QEMU 0.15.0 monitor - type 'help' for more information
(qemu) info migrate
Migration status: completed
(qemu)
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Unfortunately, migration is not working for our large VMs, having 7 CPUs
and 30720 KB of memory:
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qemu-system-x86_64 -name wip -boot c -smp 7 -m 30720 -drive
file=/dev/disk/by-path/ip-192.168.251.1:3260-iscsi-iqn.2010-09.de.tu-berlin.cit.wip-lun-0
-net nic,model=e1000,macaddr=02:59:59:59:3:E4 -net
tap,ifname=tap249,script=/etc/kvm/kvm-ifup,downscript=/etc/kvm/kvm-ifdown -k
de -vnc :30249 -monitor unix:/var/run/kvm/wip/monitor,server,nowait
-serial none -parallel none -pidfile /var/run/kvm/wip/pid
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In case of this VM, the migration process directly fails at execution
time:
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QEMU 0.15.0 monitor - type 'help' for more information
(qemu) migrate -d "exec:gzip -c > /var/run/kvm/suspend-vm-249.bin.gz"
migration failed
(qemu)
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I did quite some testing:
- the problem seems to be independend from the number of virtual cores
of the VM. Suspension of "-smp 7" fails as well as "-smp 1"
- the problem seems to be only related to the amount of memory of the
VM. Suspending "-m 30720" fails, but slightly reducing the memory of
the VM is sufficient, so that suspending is working fine. For example,
for "-m 30000" the suspending is working.
- the problem seems to affect ONLY the suspension using "exec:gzip".
Really migrating the VM to another server host using "exec:tcp..."
is working absolutely fine.
Any help is greatly appreciated.
Best,
Matthias
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