Thank you very much. It's clear now.

One more question, I see that the API of the free ESX 3i version only
support read-only operations like monitoring. When I firstly installed ESXi
and didn't use the free license, I have 60 days' evaluation and VCL could
successfully do all operations. But when I used the free license, some
features were removed and VCL could not register VM correctly.

Does it mean we should always use evaluation mode to support VCL's

2009/5/6 Brian Bouterse <>

> Regarding NFS, below are a few practical reasons to not use local hard
> disks to host the images as they run.
> 1)  Say each image is 10GB, on a 72GB hard drive (the standard "large"
> drive in a blade), that means as a maximum consolidation you can only have 7
> VM's on a blade.  A blade can likely handle between 4 - 30 VMs depending on
> how powerful it is, so this would be a gross underutilization.
> 2)  It takes a VERY long time to copy images to and from the blades (3-6
> MB/s) because of the difficult file system translation between to and from
> the VMFS filesystem format on the hypervisor.
> 3)  ESX 3i (the free, efficient hypervisor) is designed to boot as a
> disksless hypervisor, so ESX3i environments would be out which would reduce
> the number of folks who could do this dramaticlly
> 4)  Although it seems performance counter-intuative, actually if booting
> from an actual storage system with multiple disks, VMs will perform quicker
> when booting over the network.  Consider the HD thrashing that would occur
> if a single disk were really handling the I/O operations of 20VMs on a
> single hypervisor.  Believe it or not, the network is faster.
> 5)  While not possible with VCL today, if the instance images live on the
> network natively, the opportunity to do things like Vmotion aren't totally
> out of the question, but those are not at all possible with local disk boot.
> In regards to image re-using, your configuration is not correct.  It sounds
> like you need to create a few more computer "slot" entries in the computer
> table and link those slots to your hypervisor entry in the computer table.
>  The number of "slots" you have equals the number of virtual machines that
> can run concurrently.  Notice it actually copies it from
> /golden/<image_name>/ to /inuse/<slot_name>.  Once a slot is created,
> remember to associate it with a hypervisor through the "Virtual Hosts" area.
>  If you still can't get this, post up some of the lines in your computer
> table's DB.
> Best,
> Brian
> Brian Bouterse
> Secure Open Systems Initiative
> 919.698.8796
> On May 6, 2009, at 2:07 AM, 乔木 wrote:
>  Hi,
>> We have setup the environment for VM provision on ESXi recently. We are
>> confused about some mechanisms:
>>  - Images are stored in NFS
>> As I see, VCL stores images in NFS and just copy it locally when using it.
>> It means that the hardisk in the esxi hypervisor will not be used. All the
>> VMs are stored in remote computer and all the operations will be remote
>> operation (CPU exsits in Hypervisor but hardisk exsits in NFS). I think it
>> may lead performance problems. Although we can setup mutiple NFS servers,
>> it
>> is not good that the hardisk in the hypervisor is not used and all the
>> operations will be remote in my opinion. Why not transfer the image to the
>> esxi hypervisor which will run the image?
>>  - Image reusing
>> When we use an image from repository, VCL does: 1. copy the image form
>> /golden/<image_name> to /inuse/<image_name>, 2. start the image. It's
>> difficult for image reusing. It's impossible for mutiple machines to use
>> the
>> same image because the copy operation will only copy one image to the
>> /inuse
>> folder and that image can be used only for one esxi hypervisor. Other copy
>> operation will overwrite that image. Again, if we transfer the image to
>> hypervisor, there won't be such problem.
>> --
>> Best wishes,
>> 乔木
>> MOE KLINNS Lab and SKLMS Lab, Xi'an Jiaotong University
>> Department of Computer Science and Technology, Xi’an Jiaotong University
>> TEL: 15991676983
>> E-mail:

Best wishes,
MOE KLINNS Lab and SKLMS Lab, Xi'an Jiaotong University
Department of Computer Science and Technology, Xi’an Jiaotong University
TEL: 15991676983

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