LVM & Stripe
 

Hello list,

I have a question about LVM.

My server has five disks and I will use it to create a LVM environment.

I saw in the lvcreate man page that I can use the “-i� option to set
the number of disks that I want to stripe the lvols, but this option
doesn’t exists in the “lvchange� option (in case I add new disks to
the VG).

I had in mind: create 10 lvols – “lvcreate -i5 -L 10G MyVG
/dev/MyVG/lvol[1-10]� and in the future, add more disks and increate
the stripe value of the existing lvols.

Does anybody knows how to change the parameter “-i" of a lvol that
already exists?

Best Regards

Lincoln Zuljewic Silva
More contact info.: http://www.system.adm.br/contact.php

"How often must a question be asked before it’s considered a
frequently asked question?"
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LVM & Stripe
 

On Tuesday, March 09, 2010 06:40 AM, Lincoln Zuljewic Silva wrote:
> Hello list,
>
> I have a question about LVM.
>
> My server has five disks and I will use it to create a LVM environment.
>
> I saw in the lvcreate man page that I can use the “-i� option to set
> the number of disks that I want to stripe the lvols, but this option
> doesn’t exists in the “lvchange� option (in case I add new disks to
> the VG).
>
> I had in mind: create 10 lvols – “lvcreate -i5 -L 10G MyVG
> /dev/MyVG/lvol[1-10]� and in the future, add more disks and increate
> the stripe value of the existing lvols.

I would recommend md striping over lvm but then lvm is a bit more
flexible on that score if you have disks of varying size. What are you
using as your physical volumes?


>
> Does anybody knows how to change the parameter “-i" of a lvol that
> already exists?

It appears to be fixed at creation time. Kinda hard to let you mess
around with stripesize and what not after stuff has been laid out on the
platters.
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LVM & Stripe
 

On Mar 8, 2010, at 7:31 PM, Christopher Chan <christopher.chan@bradbury.edu.hk
> wrote:

> On Tuesday, March 09, 2010 06:40 AM, Lincoln Zuljewic Silva wrote:
>> Hello list,
>>
>> I have a question about LVM.
>>
>> My server has five disks and I will use it to create a LVM
>> environment.
>>
>> I saw in the lvcreate man page that I can use the “-i� option to
>> set
>> the number of disks that I want to stripe the lvols, but this option
>> doesn’t exists in the “lvchange� option (in case I add new
>> disks to
>> the VG).
>>
>> I had in mind: create 10 lvols – “lvcreate -i5 -L 10G MyVG
>> /dev/MyVG/lvol[1-10]� and in the future, add more disks and incre
>> ate
>> the stripe value of the existing lvols.
>
> I would recommend md striping over lvm but then lvm is a bit more
> flexible on that score if you have disks of varying size. What are you
> using as your physical volumes?

I actually like mdraid for raid1s then striping them with LVM for
raid10s and it has the added benefit of passing the config to the file
system during mkfs so it sets the chunk size and stripe width
appropriately.

>>
>> Does anybody knows how to change the parameter “-i" of a lvol that
>> already exists?
>
> It appears to be fixed at creation time. Kinda hard to let you mess
> around with stripesize and what not after stuff has been laid out on
> the
> platters.

Yeah, unfortunately you can't change the interleave of a LV. You need
to keep around 20% in reserve so when you add another PV you can
create a new LV with the new interleave and then copy or dump/restore
from the old LV to the new, delete the old LV, and repeat for the
other LVs in the group. Remember to start with your largest to your
smallest LVs.

-Ross


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LVM & Stripe
 

Christopher and Ross,

Thanks for the tips. I will make some tests using md and check performance.

Unfortunately I can't move the data to another LV to setup a new
stripe value when a new PV is added.

Thanks

Lincoln

On Mon, Mar 8, 2010 at 10:43 PM, Ross Walker <rswwalker@gmail.com> wrote:
> On Mar 8, 2010, at 7:31 PM, Christopher Chan <christopher.chan@bradbury.edu.hk
> Â*> wrote:
>
>> On Tuesday, March 09, 2010 06:40 AM, Lincoln Zuljewic Silva wrote:
>>> Hello list,
>>>
>>> I have a question about LVM.
>>>
>>> My server has five disks and I will use it to create a LVM
>>> environment.
>>>
>>> I saw in the lvcreate man page that I can use the “-i� option to
>>> set
>>> the number of disks that I want to stripe the lvols, but this option
>>> doesn’t exists in the “lvchange� option (in case I add new
>>> disks to
>>> the VG).
>>>
>>> I had in mind: create 10 lvols – “lvcreate -i5 -L 10G MyVG
>>> /dev/MyVG/lvol[1-10]� and in the future, add more disks and incre
>>> ate
>>> the stripe value of the existing lvols.
>>
>> I would recommend md striping over lvm but then lvm is a bit more
>> flexible on that score if you have disks of varying size. What are you
>> using as your physical volumes?
>
> I actually like mdraid for raid1s then striping them with LVM for
> raid10s and it has the added benefit of passing the config to the file
> system during mkfs so it sets the chunk size and stripe width
> appropriately.
>
>>>
>>> Does anybody knows how to change the parameter “-i" of a lvol that
>>> already exists?
>>
>> It appears to be fixed at creation time. Kinda hard to let you mess
>> around with stripesize and what not after stuff has been laid out on
>> the
>> platters.
>
> Yeah, unfortunately you can't change the interleave of a LV. You need
> to keep around 20% in reserve so when you add another PV you can
> create a new LV with the new interleave and then copy or dump/restore
> from the old LV to the new, delete the old LV, and repeat for the
> other LVs in the group. Remember to start with your largest to your
> smallest LVs.
>
> -Ross
>
>
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
>



--
Lincoln Zuljewic Silva
More contact info.: http://www.system.adm.br/contact.php

"How often must a question be asked before it’s considered a
frequently asked question?"
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