Install a VM into a file or a LV ?

Install a VM into a file or a LV ?

[Lentes, Bernd]

Hi,

I'm new to this list and i hope this is the right list for my question. I like to create several VM's using KVM on a SLES 11 SP1 host. What is better/faster ? Install the VM into a file or a logical Volume ? If i chosse to install it into a LV: does the LV needs a Filesystem, and does it has to be mounted ? My aim is that i want to create a HA-Cluster. For every service (currently 3) i'd like to create a VM. I want to have two hosts/nodes, both running SLES 11 SP1. I want to use DRBD to replicate the File/LV to the passive node. Do you thing that's a good solution ?

Thanks for any answer.


Bernd

Re: Install a VM into a file or a LV ?

[Avi Kivity]

On 01/05/2011 02:27 PM, Lentes, Bernd wrote:
> Hi,
>
> I'm new to this list and i hope this is the right list for my question. I like to create several VM's using KVM on a SLES 11 SP1 host. What is better/faster ?

Logical volumes are faster.

> Install the VM into a file or a logical Volume ? If i chosse to install it into a LV: does the LV needs a Filesystem, and does it has to be mounted ?

No, the volume becomes the guest's disk (which it can then paritition, 
set up logical volumes, and mount filesystems on).

> My aim is that i want to create a HA-Cluster. For every service (currently 3) i'd like to create a VM. I want to have two hosts/nodes, both running SLES 11 SP1. I want to use DRBD to replicate the File/LV to the passive node. Do you thing that's a good solution ?
>

Sure, this can work, just be sure to test it extensively.  Roll-your-own 
solutions often aren't.

-- 
error compiling committee.c: too many arguments to function

RE: Install a VM into a file or a LV ?

[Lentes, Bernd]

Avi Kivity wrote:
> On 01/05/2011 02:27 PM, Lentes, Bernd wrote:
> > Hi,
> >
> > I'm new to this list and i hope this is the right list for 
> my question. I like to create several VM's using KVM on a 
> SLES 11 SP1 host. What is better/faster ?
> 
> Logical volumes are faster.
> 
> > Install the VM into a file or a logical Volume ? If i 
> chosse to install it into a LV: does the LV needs a 
> Filesystem, and does it has to be mounted ?
> 
> No, the volume becomes the guest's disk (which it can then 
> paritition, set up logical volumes, and mount filesystems on).
> 
Hi Avi,

Thanks for the quick answer. Just to be sure:
>From the host's point of view, the LV has no filesystem and does not have to be mounted ?


Bernd

Re: Install a VM into a file or a LV ?

[Avi Kivity]

On 01/05/2011 03:35 PM, Lentes, Bernd wrote:
> Thanks for the quick answer. Just to be sure:
>  From the host's point of view, the LV has no filesystem and does not have to be mounted ?
>

Correct.  You assign it with the command

   qemu-kvm -drive file=/dev/mapper/volgroupname-lvname,cache=none

-- 
error compiling committee.c: too many arguments to function

Re: Install a VM into a file or a LV ?

[Reeted]

On 01/05/2011 02:08 PM, Avi Kivity wrote:
>
>> My aim is that i want to create a HA-Cluster. For every service 
>> (currently 3) i'd like to create a VM. I want to have two 
>> hosts/nodes, both running SLES 11 SP1. I want to use DRBD to 
>> replicate the File/LV to the passive node. Do you thing that's a good 
>> solution ?
>>
>
> Sure, this can work, just be sure to test it extensively.  
> Roll-your-own solutions often aren't.
>

Often aren't what?

Do you consider DRBD a roll-your-own solution or a standard one?

(I suppose the opposite of "roll-your-own" is "standard"...)

Thank you

Re: Install a VM into a file or a LV ?

[Avi Kivity]

On 01/05/2011 04:26 PM, Reeted wrote:
> On 01/05/2011 02:08 PM, Avi Kivity wrote:
>>
>>> My aim is that i want to create a HA-Cluster. For every service 
>>> (currently 3) i'd like to create a VM. I want to have two 
>>> hosts/nodes, both running SLES 11 SP1. I want to use DRBD to 
>>> replicate the File/LV to the passive node. Do you thing that's a 
>>> good solution ?
>>>
>>
>> Sure, this can work, just be sure to test it extensively.  
>> Roll-your-own solutions often aren't.
>>
>
> Often aren't what?

Tested extensively.

>
> Do you consider DRBD a roll-your-own solution or a standard one?
>
> (I suppose the opposite of "roll-your-own" is "standard"...)

I have no experience or knowledge about DRBD.  I'm more concerned about 
the code that detects failure and switches things over, and makes sure 
the guest isn't running on both nodes, etc.

-- 
error compiling committee.c: too many arguments to function

Re: Install a VM into a file or a LV ?

[Ben Beuchler]

Take a look at Ganeti.  It is designed to do exactly what you
describe:  HA VMs sharing their LV-backed disks over DRBD.

-Ben

> I'm new to this list and i hope this is the right list for my question. I like to create several VM's using KVM on a SLES 11 SP1 host. What is better/faster ? Install the VM into a file or a logical Volume ? If i chosse to install it into a LV: does the LV needs a Filesystem, and does it has to be mounted ? My aim is that i want to create a HA-Cluster. For every service (currently 3) i'd like to create a VM. I want to have two hosts/nodes, both running SLES 11 SP1. I want to use DRBD to replicate the File/LV to the passive node. Do you thing that's a good solution ?
>
> Thanks for any answer.
>
>
> Bernd
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