Ruslan Sivak wrote:

Does it just require a kernel recompile? Is there maybe one available somewhere?

No it requires changes to the kernel itself, changes which I don't think Red Hat will introduce in a minor release as their current VM stuff is Xen based which has it's own paravirtualization support in the existing kernel(pre VMI). I read that Red Hat is moving towards KVM though, I don't have any knowledge on that project, maybe it uses VMI as well.

Would it give me improved disk access speed?

I doubt it. I'm planning on using it mainly so I can run a couple of NTP servers in VMs. Even though it's still not officially supported my experience shows that NTP *will never sync* in VMWare with normal virtualization. But with VMI/paravirtualization I've had a ntp daemon synced for weeks so far. I don't plan to use VMI for anything other then a couple bare bones VMs to run NTP. Then the rest of the VMs will run ntpdate every minute against them, and the non VMs will run ntp daemons and sync with them. The internal vmware time sync(at least in ESX) doesn't work too well in my experience so I just turn it off and use ntpdate instead.

Disk access speed is limited to the speed of the I/O subsystem. VMware has recently demonstrated a ESX system being able to sustain 100,000 I/Os per second (maxing out ~500 15k RPM disks), and that wasn't using paravirtualization. If you can get 100k IOPS with normal virtualization...

nate

Hello,

"nate" centos@linuxpowered.net schreef in bericht news:4582.65.102.144.193.1215733640.squirrel@webmail.linuxpowered.net... Ruslan Sivak wrote:

I'm using VMWare Server 2 RC1 to on top of CentOS 5.2 x86_64 running a CentOS 5.2 i386 guest. I have enabled VMI in VMware, so I guess it won't let me install if VMI wasn't available in the kernel? How do I know whether VMI is supported/enabled and what performance benefits can I expect from it? I'm still not getting full hard drive speeds (only getting about 1/3 when using hdparm -t ).

I don't believe it is supported in CentOS 5.x. I am using Fedora Core 8 for VMI support.

[root@dc1-ntp001:~]# dmesg | grep -i vmi VMI: Found VMware, Inc. Hypervisor OPROM, API version 3.0, ROM version 1.0 vmi: registering clock event vmi-timer. mult=7809995 shift=22 Booting paravirtualized kernel on vmi vmi: registering clock source khz=1862048 Time: vmi-timer clocksource has been installed.

I suspect it will be in RHEL/CentOS 6.x

nate

Indeed, It's not in the EL5 kernel, but I hope that Redhat backport the VMI 3.0 patch for Update 3. It Can be done, SuSE did it with SLES10 SP2 and kernel 2.6.16.

Maybe some one with enough kernel knowledge can try to integrate the Novell / SuSE patches in EL5 2.6.18 kernel. SLES 10 src.rpm kernels are available at ftp://ftp.suse.com/pub/projects/kernel/kotd/SLES10_SP2_BRANCH/ Eventually it maybe an addition for the plus repo.

But, I'm afraid that I don't have the knowledge to pull this off ....:(

The easiest way to get VMI support, is to rebuild the latest FC7 (2.6.23.xx) kernel, It compiles and installs correctly on CentOS5.2. It will complain about a to old mkinitrd, but with an forced install, it will create a correct initrd. The later FC8 needs also and updated / backported new mkinitrd, and updated Vmware-tools. The Vmware tools included with ESX3.5 update 1 won't compile on kernel 2.6.25. This is an known issue. Rumours go that the Vmware-tools in latest Server packages are 2.6.25 compatible, but I haven't tested that

I tested rebuild FC7 kernel with an test VM in ESX 3.5. It runs OK.

John .