[linux-lvm] LV's above 2TB, PV's above 1TB, LBD?

[linux-lvm] LV's above 2TB, PV's above 1TB, LBD?

[Tad Kollar]

Using LVM2 tools from CVS, and kernel 2.5.47 w/dm patches...

Seems to be a sign error someplace... 2+ TB requests are treated as 4+ TB:

lvm> lvextend -l 10980 /dev/vgtest2/lvtest2
   Extending logical volume lvtest2 to 2.68 TB
   logical volumes cannot be larger than 4.00 TB

Also, pvcreate treats 1+ TB devices as 2+ TB and rejects them.

Aside from this, now that the 2.5 kernel supports LBD's, can the limit on LV's 
be raised to 16 TB?

Thanks,
Tad

Re: [linux-lvm] LV's above 2TB, PV's above 1TB, LBD?

[Alasdair G Kergon]

On Thu, Nov 14, 2002 at 09:10:58AM -0500, Tad Kollar wrote:
> lvm> lvextend -l 10980 /dev/vgtest2/lvtest2
>    Extending logical volume lvtest2 to 2.68 TB
>    logical volumes cannot be larger than 4.00 TB
A missing division by 2 when producing the error message:-)
 
> Also, pvcreate treats 1+ TB devices as 2+ TB and rejects them.
Maybe another missing factor of 2 somewhere?
Can you provide some *specific* output demonstrating this problem
(like you did for the first problem)?
 
> Aside from this, now that the 2.5 kernel supports LBD's, can the limit
> on LV's be raised to 16 TB?
For the *new* format of metadata (in beta 4 released today), yes: 
for now, I've knocked out the LV size restriction in CVS.  Further
tweaks to the tools may also be required. Please try it and let us
know whether it works, or what else needs changing.
 
Alasdair
-- 
agk@uk.sistina.com

Re: [linux-lvm] LV's above 2TB, PV's above 1TB, LBD?

[Ragnar Kjørstad]

On Mon, Nov 18, 2002 at 04:37:28PM +0000, Alasdair G Kergon wrote:
> > Aside from this, now that the 2.5 kernel supports LBD's, can the limit
> > on LV's be raised to 16 TB?
> For the *new* format of metadata (in beta 4 released today), yes: 
> for now, I've knocked out the LV size restriction in CVS.  Further
> tweaks to the tools may also be required. Please try it and let us
> know whether it works, or what else needs changing.

Is the new metdata format really required?
Isn't the unit used in the metadata PEs? So should it not work with the
old format if only the PEs are large enough?



-- 
Ragnar Kjørstad
Big Storage

Re: [linux-lvm] LV's above 2TB, PV's above 1TB, LBD?

[Heinz J . Mauelshagen]

On Mon, Nov 18, 2002 at 05:51:42PM +0100, Ragnar Kjørstad wrote:
> On Mon, Nov 18, 2002 at 04:37:28PM +0000, Alasdair G Kergon wrote:
> > > Aside from this, now that the 2.5 kernel supports LBD's, can the limit
> > > on LV's be raised to 16 TB?
> > For the *new* format of metadata (in beta 4 released today), yes: 
> > for now, I've knocked out the LV size restriction in CVS.  Further
> > tweaks to the tools may also be required. Please try it and let us
> > know whether it works, or what else needs changing.
> 
> Is the new metdata format really required?
> Isn't the unit used in the metadata PEs? So should it not work with the
> old format if only the PEs are large enough?

The constraint in the LVM1 format is ~2^16 physical extents maximum.
If we support more than this amount, we'ld be LVM1 format incompatible.
Going beyond that constraint is possible with the new format Alasdair was
refering to but you loose LVM1 format compatibility.
IOW: no way back to running such configuration with LVM1.

But yes, with larger physical extent sizes _and_ less than ~2^16 extents
maximum you can stay with LVM1 format in order to be backwards compatible.

> 
> 
> 
> -- 
> Ragnar Kjørstad
> Big Storage
> 
> _______________________________________________
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> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen@Sistina.com                           +49 2626 141200
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