Hello Kirill, Am Thu, 1 Dec 2011 21:27:49 +0400 schrieb Kirill Korotaev <d...@parallels.com>:
> That's most likely due to a single file system used for containers - > journal becomes a bottleneck. fsync forces journal flushes and other > workloads begin to wait for journal... In reality workload looks like > this are typical for heavy loaded databases or mail systems only. > > How to improve: > - increase journal size > - split file systems, i.e. run each container from it's own file > system I've created another lv with an ext4 filesystem with maximum journal-size and mounted this filesystem under /var/lib/vz/private/<VID>. I will call this vm as VM-sep. All other vhosts where kept inside the volume as before. Than I start stressing the VM-sep and tested the impact to the other VMs. It was exactly the same as if I run all VMs on the same partition. There was indeed a difference, when I stress the Host itself. If I do filesystem stress in the same Partition (/var/lib/vz) The perfomance of VM is much worse (similar to stress in a VM, a little better) than if I would stress in a completly different Partition (/var/tmp in my case) To get some Numbers: (not very sientific, but good for a measure) Throughput of a Webserver in a VM called VM-web in KB/s: * without stress 101.9 * stress /var/tmp on host 24.3 * stress /var/lib/vz on Host 10.5 * stress a vm, not VM-web, same fs 8.3 * stress VM-sep 7.6 Maybe the Diskencryption plays a role, maybe there is something in the VM-Isolation layer, I have no clue. But as you mentione before this workload is typical for heavy loaded databases or mail systems only. Neither of this application will run in my vm-environment. So I will ignore this. Greetings, Hubert > On Nov 29, 2011, at 20:13 , Hubert Krause wrote: > > my environment is a Debian squeeze host with a few debian squeeze > > guests. The private and root filesystems of the guest are locatet on > > the same raid device (raid5) in an luksCrypt Container in an LVM > > container on an ext4 partition with nodelalloc as mountoption. If I > > run the tool stress: > > > > stress --io 5 --hdd 5 --timeout 60s (which means fork 5 threads > > doing read/write access and 5 threads doing constantly fsync) the > > responsivness of the other VMs is very bad. That means, Isolation > > for IO operations is not given. I've tried to reduce the impact of > > the VM with 'vzctl set VID --ioprio=0'. There was only a > > minor effect, my application on the other VM where still not > > responsive. > > > > Any Idea how to prevent a single VM to disturb the other VMs > > regarding diskIO? -- Dr. Hubert Krause Geschäftsbereich Risk & Fraud INFORM GmbH, Pascalstr. 23, 52076 Aachen, Germany Tel. (+49)2408 9456 5145 e-mail: hubert.kra...@inform-software.com, http://www.inform-software.de/ INFORM Institut fur Operations Research und Management GmbH Registered AmtsG Aachen HRB1144 Gfhr.Adrian Weiler _______________________________________________ Users mailing list Users@openvz.org https://openvz.org/mailman/listinfo/users