kvm vm freezes sometimes

[copymaster]

hi

in my cluster environment i did several tests and today i recognized the following (mysterious) things:

1)
When installing a kvm (w2k3) on an iscsi/lvm, the vm has good performance, installation is fast.

2)
When installing a kvm (w2k3) on local storage (velocy raptor 10000RPM), the vm freezes every now and then for 1-5 seconds. Installation is slow and overal performance sucks.

3)
Resizing qemu images is a great feature and it works perfectly but needs a lot of time

4)
Network performance on all types of VM (iscsi or local) is only about 70% from real network speed. Is that correct? I tried virtio, e1000 and rtl8139


Can anybody confirm the bad performance on local storage? Where do i have to search the problem? maybe the raidcontroller?
3ware Inc 9690SA SAS/SATA-II RAID PCIe (rev 01)

i am now testing the local vm's (w2k3) using qcow2 hdd's.

 

[tom]

hi

in my cluster environment i did several tests and today i recognized the following (mysterious) things:

1)
When installing a kvm (w2k3) on an iscsi/lvm, the vm has good performance, installation is fast.

2)
When installing a kvm (w2k3) on local storage (velocy raptor 10000RPM), the vm freezes every now and then for 1-5 seconds. Installation is slow and overal performance sucks.

3)
Resizing qemu images is a great feature and it works perfectly but needs a lot of time

4)
Network performance on all types of VM (iscsi or local) is only about 70% from real network speed. Is that correct? I tried virtio, e1000 and rtl8139


Can anybody confirm the bad performance on local storage? Where do i have to search the problem? maybe the raidcontroller?
3ware Inc 9690SA SAS/SATA-II RAID PCIe (rev 01)

i am now testing the local vm's (w2k3) using qcow2 hdd's.

to compare results on local disks you should use raw instead of qcow2. (with qcow2 you have an additional virtualization level). i generally suggest using raw.

a basic test of local storage performance:
pveperf

but only run if the system is not under load, post the results here.

raid controller: always make sure you have raid controller cache enabled (write back) and use always a BBU for protection of power failure.

 

[tom]

hi

in my cluster environment i did several tests and today i recognized the following (mysterious) things:

1)
When installing a kvm (w2k3) on an iscsi/lvm, the vm has good performance, installation is fast.

2)
When installing a kvm (w2k3) on local storage (velocy raptor 10000RPM), the vm freezes every now and then for 1-5 seconds. Installation is slow and overal performance sucks.

3)
Resizing qemu images is a great feature and it works perfectly but needs a lot of time

4)
Network performance on all types of VM (iscsi or local) is only about 70% from real network speed. Is that correct? I tried virtio, e1000 and rtl8139


Can anybody confirm the bad performance on local storage? Where do i have to search the problem? maybe the raidcontroller?
3ware Inc 9690SA SAS/SATA-II RAID PCIe (rev 01)

i am now testing the local vm's (w2k3) using qcow2 hdd's.

regarding the network performance:
if want to optimize this I suggest you take a look on the KVM mailing list - here you will find hints to get more performance. but for most setups, the defaults are quite usable.

 

[copymaster]

Thank you.

it seems to bee the raid controller. I did not enable write cache because i have no BBU. But without enabled write cache, the system hangs. Now i enabled the cache even though i do not have a BBU. And it runs like a charm.

Seems that i have to order a few BBU's....

 

[udo]

Hi,
like tom wrote above - try also local the raw-format.
shut down the vm and than convert the qcow-file with qemu-img.
After that edit the conf-file of the vm, so that the raw-files are in use.

Your small Value as fsyncs/sec looks like your cache of the raidcontroller is not enabled.
( i have FSYNCS/SECOND: 4766.50)

Udo