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From Bjoern Teipel <>
Subject Re: diskless boot
Date Tue, 19 Mar 2013 03:50:17 GMT
On 3/18/2013 8:43 AM, Donal Lafferty wrote:
> AFAIK, data disks are by default created in Primary Storage and not on the hypervisor
itself.  I take it you want the replacement server for a VM to sit in a different cluster
that does not have access to the same primary storage
> Did you mean to ask whether the data disk is a 'dyanmic' hard drive image?  'Dynamic'
disks are about as large as the actual data stored on it.  They do not reserve spaced in the
store for portions of the disk that have no data.  In this case, I do not know the answer,
as I've not much experience with KVM.
No I was more talking about the thin provisioning at LVM because I was 
considering to boot those disk less VMs with the 1GB data disk on hyper 
visor with local storage not to
waste precious NAS.
That's why I was thinking of thin provisioning of LVM
> IIRC, 'thin' as in 'thin provisioning' relates to templates.  To reduce the foot print
of the root device, a read/write 'diff' disk is created and linked to a read only 'base' disk.
 The 'base' disk is a copy of the template image.  The diff captures changes, and grows over
time as the VM updates.  Because a number of VMs use the same 'base' image, template transfer
time and the foot print of the root device is substantially reduced.
That's the reason why we have patchdisk files ?
> -----Original Message-----
> From: Teipel, Bjoern []
> Sent: 18 March 2013 3:24 PM
> To:
> Cc:
> Subject: Re: diskless boot
> Hi Donal,
> I didn't try thin provisioning on a local LVM disk but I would expect that is takes only
few MB. Does CS support thin on local storage (LVM)?
> I can see where you question is going but a data disk,even empty would create a dependency
to the hypervisor.
> The idea for using disk less boot is not to create any dependency on storage and only
rely on memory/CPU. If the hypervisor goes down I just start the VM in a new one.
> A data disk would be here blocking and you have to remove the data disk from the VM before
you can do any action on the VM. Doubt that would work in CS.
> Bjoern
> On Mar 18, 2013, at 4:00 AM, "Donal Lafferty" <> wrote:
>> Let me rephrase that,
>> Hi Bjoern,
>> On the KVM deployment you are using, I take it that the 1 gig disk is a data disk.
 It the problem that its unwieldy to manage or that 1 gig takes up too much room?
>> Does the 1 gig data disk take up a lot of space on the primary storage?
>> DL
>>> -----Original Message-----
>>> From: Mathias Mullins []
>>> Sent: 18 March 2013 10:53 AM
>>> To:
>>> Subject: Re: diskless boot
>>> Thin or thick provisioned? On what type of file system?
>>> Thank you,
>>> Matt
>>> On Mar 18, 2013, at 9:47 PM, "Donal Lafferty" <>
>>> wrote:
>>>> Out of interest, how much space does an unused 1 Gig disk take up on a
>>> hypervisor?
>>>> DL
>>>>> -----Original Message-----
>>>>> From: Bjoern Teipel []
>>>>> Sent: 16 March 2013 6:12 AM
>>>>> To:
>>>>> Subject: diskless boot
>>>>> Hi guys,
>>>>> one of my questions is still open:
>>>>> - CS doesn't support booting over ISO only without attaching a disk.
>>>>>    Background is, we migrate our datacenter to boot from ISO/PXE and
>>>>>    thats a big no go for me if I'm enforced to assign a 1G disk.
>>>>>    Also set the minimum disk size to 0G in the global settings but
>>>>>    I can't create "No Disk" Disk offerings ...
>>>>> Nobody had the desire to boot disk less other than me ?
>>>>> Can't believe that ;-)
>>>>> Thanks,
>>>>> Bjoern

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