[linux-lvm] lvm on a single big partition or just a single big partition?

[linux-lvm] lvm on a single big partition or just a single big partition?

[Zhengquan Zhang]

Hello lvm list,

Though I have used lvm for some time, I have one question that I don't
understand.

For one harddrive I often create a /boot parition that is not lvm and
create a huge partition on the rest of the harddrive for PV of lvm. Now
I am thinking what is the difference between doing partition like this
and just a single big partition without lvm?

Thanks in advance,

-- 
Zhengquan

Re: [linux-lvm] lvm on a single big partition or just a single big partition?

[Stuart D. Gathman]

On Wed, 3 Jun 2009, Zhengquan Zhang wrote:

> For one harddrive I often create a /boot parition that is not lvm and
> create a huge partition on the rest of the harddrive for PV of lvm. Now
> I am thinking what is the difference between doing partition like this
> and just a single big partition without lvm?

With LVM, you can create many logical volumes.  If you only ever create one
logical volume that fills the entire PV, and you aren't spanning drives
(multiple PVs) or mirroring, then LVM is not doing anything for you.

Even with just one LV, leave some space for a snapshot.  Then you can
take more consistent backups by creating a snapshot of your main LV
and backing that up instead.  Put your swap space in LVM as well.

One reason to create multiple LVs is for virtual machines.  If you
run Xen, VMWare, or other virtual machine, then each virtual machine
should have its own LVs for disk drives.  This is more efficient
than using a filesystem file for a virtual disk.

PS.  I wonder if Grub will ever support LVM?  Does LILO work with LVM?

-- 
	      Stuart D. Gathman <stuart@bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

Re: [linux-lvm] lvm on a single big partition or just a single big partition?

[Zhengquan Zhang]

On Wed, Jun 03, 2009 at 02:42:29PM -0400, Stuart D. Gathman wrote:
> On Wed, 3 Jun 2009, Zhengquan Zhang wrote:
> 
> > For one harddrive I often create a /boot parition that is not lvm and
> > create a huge partition on the rest of the harddrive for PV of lvm. Now
> > I am thinking what is the difference between doing partition like this
> > and just a single big partition without lvm?
> 
> With LVM, you can create many logical volumes.  If you only ever create one
> logical volume that fills the entire PV, and you aren't spanning drives
> (multiple PVs) or mirroring, then LVM is not doing anything for you.

That is what I am doing, so I am not fully utilizing lvm. another
question, is it advisable to create on pv for one harddrive? 

> 
> Even with just one LV, leave some space for a snapshot.  Then you can
> take more consistent backups by creating a snapshot of your main LV
> and backing that up instead.  Put your swap space in LVM as well.

Thanks for pointing out this. I never thought of leaving space for
snapshot. and the swap too, why it is good to put swap in lvm?

> 
> One reason to create multiple LVs is for virtual machines.  If you
> run Xen, VMWare, or other virtual machine, then each virtual machine
> should have its own LVs for disk drives.  This is more efficient
> than using a filesystem file for a virtual disk.

Oh really, I never thought about this, so virtual machine can directly
use lv for the as their filesystem?

> 
> PS.  I wonder if Grub will ever support LVM?  Does LILO work with LVM?

As I know, LILO does, buy anyway we've got separate /boot.

Thanks a lot Stuart, it helped me a lot,

-- 
Zhengquan

Re: [linux-lvm] lvm on a single big partition or just a single big partition?

[Tomasz Chmielewski]

Stuart D. Gathman wrote:

> PS.  I wonder if Grub will ever support LVM?  Does LILO work with LVM?

Grub2 is supposed to support LVM.


-- 
Tomasz Chmielewski
http://wpkg.org

Re: [linux-lvm] lvm on a single big partition or just a single big partition?

[Marian Csontos]

Zhengquan Zhang wrote:
> On Wed, Jun 03, 2009 at 02:42:29PM -0400, Stuart D. Gathman wrote:
>   
>> On Wed, 3 Jun 2009, Zhengquan Zhang wrote:
>>
>>     
>>> For one harddrive I often create a /boot parition that is not lvm and
>>> create a huge partition on the rest of the harddrive for PV of lvm. Now
>>> I am thinking what is the difference between doing partition like this
>>> and just a single big partition without lvm?
>>>       
>> With LVM, you can create many logical volumes.  If you only ever create one
>> logical volume that fills the entire PV, and you aren't spanning drives
>> (multiple PVs) or mirroring, then LVM is not doing anything for you.
>>     
Not at the moment, but the moment you run out of space and decide to add 
another drive, it will save you a lot of trouble moving all your 
partitions around...
> That is what I am doing, so I am not fully utilizing lvm. another
> question, is it advisable to create on pv for one harddrive? 
>
>   
Yes, it is the right way. Having 2 PVs on single drive offer no benefit 
I can think of, and actually it is a step back - you can not share "free 
space" between PVs, thus it is a way to simulate old fashioned partitions.
>> Even with just one LV, leave some space for a snapshot.  Then you can
>> take more consistent backups by creating a snapshot of your main LV
>> and backing that up instead.  Put your swap space in LVM as well.
>>     
>
> Thanks for pointing out this. I never thought of leaving space for
> snapshot. and the swap too, why it is good to put swap in lvm?
>
>   
I think most of installers do not think of it neither (unless you 
partition you disk yourself, which is not so difficult, but may be a bit 
scary for newbies) - I would like an install option "leave N% of created 
PV free and use only the rest now".
>> One reason to create multiple LVs is for virtual machines.  If you
>> run Xen, VMWare, or other virtual machine, then each virtual machine
>> should have its own LVs for disk drives.  This is more efficient
>> than using a filesystem file for a virtual disk.
>>     
>
> Oh really, I never thought about this, so virtual machine can directly
> use lv for the as their filesystem?
>
>   
>> PS.  I wonder if Grub will ever support LVM?  Does LILO work with LVM?
>>     
>
> As I know, LILO does, buy anyway we've got separate /boot.
>
> Thanks a lot Stuart, it helped me a lot,
>
>   

Re: [linux-lvm] lvm on a single big partition or just a single big partition?

[Zhengquan Zhang]

On Fri, Jun 05, 2009 at 10:00:00AM +0200, Marian Csontos wrote:
> Zhengquan Zhang wrote:
>> On Wed, Jun 03, 2009 at 02:42:29PM -0400, Stuart D. Gathman wrote:
>>   
>>> On Wed, 3 Jun 2009, Zhengquan Zhang wrote:
>>>
>>>     
>>>> For one harddrive I often create a /boot parition that is not lvm and
>>>> create a huge partition on the rest of the harddrive for PV of lvm. Now
>>>> I am thinking what is the difference between doing partition like this
>>>> and just a single big partition without lvm?
>>>>       
>>> With LVM, you can create many logical volumes.  If you only ever create one
>>> logical volume that fills the entire PV, and you aren't spanning drives
>>> (multiple PVs) or mirroring, then LVM is not doing anything for you.
>>>     
> Not at the moment, but the moment you run out of space and decide to add  
> another drive, it will save you a lot of trouble moving all your  
> partitions around...

Sounds great and definetely I will exploit this feature in the future.

>> That is what I am doing, so I am not fully utilizing lvm. another
>> question, is it advisable to create on pv for one harddrive? 
>>
>>   
> Yes, it is the right way. Having 2 PVs on single drive offer no benefit  
> I can think of, and actually it is a step back - you can not share "free  
> space" between PVs, thus it is a way to simulate old fashioned 
> partitions.

Thanks for confirming.

>>> Even with just one LV, leave some space for a snapshot.  Then you can
>>> take more consistent backups by creating a snapshot of your main LV
>>> and backing that up instead.  Put your swap space in LVM as well.
>>>     
>>
>> Thanks for pointing out this. I never thought of leaving space for
>> snapshot. and the swap too, why it is good to put swap in lvm?
>>
>>   
> I think most of installers do not think of it neither (unless you  
> partition you disk yourself, which is not so difficult, but may be a bit  
> scary for newbies) - I would like an install option "leave N% of created  
> PV free and use only the rest now".

Yeah, that would be great, for some installer I guess there are expert
mode which enables you to do more manipulation.

Thanks, Marian,

-- 
Zhengquan