Proxmox does it quite nicely using LVM ontop of iSCSI targets - the LVM locking only allows an LV to be accessed by one host at a time, but if its deactivated on one host it can be reactivated on another
http://pve.proxmox.com/wiki/Storage_Model#LVM_Groups_with_Network_Backing On 10 March 2011 21:02, <jurgen.depic...@let.be> wrote: > Hi all. > > Presently, 7 VMs (4 windows, 3 ubuntu) are using the same nfs pool. The > machine serving that NFS pool (VLET1) has high load as soon as there is some > continuous disk activity: > > top - 13:25:30 up 23:16, 5 users, load average: 4.51, 4.41, 3.98 > Tasks: 191 total, 1 running, 189 sleeping, 0 stopped, 1 zombie > Cpu0 : 3.0%us, 2.6%sy, 0.0%ni, 44.6%id, 49.8%wa, 0.0%hi, 0.0%si, > 0.0%st > Cpu1 : 4.2%us, 2.9%sy, 0.0%ni, 54.2%id, 38.1%wa, 0.0%hi, 0.6%si, > 0.0%st > Cpu2 : 3.6%us, 2.3%sy, 0.0%ni, 55.4%id, 38.7%wa, 0.0%hi, 0.0%si, > 0.0%st > Cpu3 : 2.9%us, 4.2%sy, 0.0%ni, 56.4%id, 36.5%wa, 0.0%hi, 0.0%si, > 0.0%st > > It's a quad-core Xeon, running SW Raid on sataII disks: > cat /proc/mdstat > Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] > [raid4] [raid10] > md0 : active raid1 sdb1[1] sda1[0] > 966796224 blocks [2/2] [UU] > > When the VM client's disk activity is low, the load on VLET1 is very > minimal: > top - 13:53:30 up 23:44, 5 users, load average: 0.11, 0.81, 1.83 > Tasks: 191 total, 1 running, 189 sleeping, 0 stopped, 1 zombie > Cpu0 : 1.0%us, 2.0%sy, 0.0%ni, 92.1%id, 4.6%wa, 0.0%hi, 0.3%si, > 0.0%st > Cpu1 : 2.2%us, 5.3%sy, 0.0%ni, 90.7%id, 1.9%wa, 0.0%hi, 0.0%si, > 0.0%st > Cpu2 : 4.2%us, 3.6%sy, 0.0%ni, 87.7%id, 4.5%wa, 0.0%hi, 0.0%si, > 0.0%st > Cpu3 : 3.2%us, 3.2%sy, 0.0%ni, 93.3%id, 0.3%wa, 0.0%hi, 0.0%si, > 0.0%st > > What can I do to reduce the load? Now, sometimes a VM refuses to come up > (windows blue screen) except when I launch it on the same host (VLET1) > hosting the nfs share. After booting the VM, I can live migrate it to > another VM host, eg VLET2. > I did spot an error in /var/log/messages at boot failure of the windows VM > when starting it on VLET2: > Mar 10 11:06:46 VLET2 libvirtd: 11:06:46.137: warning : > qemudParsePCIDeviceStrs:1422 : Unexpected exit status '1', qemu probably > failedbut I'm not sure this is related. > > This is a test config; our company's mail server will soon be running in > this cluster of KVM hosts (VLET1 and VLET2 will be joined by VLET3 next > week). Since the Domino mail server is very disk intensive, I'm a bit > worried now. I would rather not run it on local disks, sionce this makes > live migration impossible. I'll need to decide where to put the storage > pool, and using which protocol (NFS or iSCSI). > > Which brings me to my last question: I was wondering whether it would be > better to use iSCSI instead of NFS? I started with this, but couldn't get a > pool defined through virt-manager (it always showed as 100% full, even when > I created a completely new iSCSI target/lun). According to e.g. > http://communities.vmware.com/thread/150775 it doesn't seem to make much > difference, whether I use iSCSI or NFS, performance-wise. Anyhow, I don't > grasp how KVM running on different hosts, connected to the same iSCSI LUN, > can work? It corrupts data, having the same LUN mounted on different > hosts... I obviously understood something wrong about iSCSI... > > Regards, Jürgen > > -- > ubuntu-server mailing list > ubuntu-server@lists.ubuntu.com > https://lists.ubuntu.com/mailman/listinfo/ubuntu-server > More info: https://wiki.ubuntu.com/ServerTeam > -- Adon Metcalfe Labyrinth Data Services Pty Ltd http://www.labyrinthdata.net.au
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