Re: [linux-lvm] How do you create large numbers of LVs? (In the 1000s) Is it even possible?

From: Jonathan E Brassow <jbrassow@redhat.com>
To: LVM general discussion and development <linux-lvm@redhat.com>,
	mingz@ele.uri.edu
Subject: Re: [linux-lvm] How do you create large numbers of LVs? (In the 1000s) Is it even possible?
Date: Thu, 28 Jul 2005 15:32:46 -0500	[thread overview]
Message-ID: <511428deb4d089c0e0d213b7e81a9fe7@redhat.com> (raw)
In-Reply-To: <1122578286.9888.47.camel@localhost.localdomain>

I think the problem you are seeing is similar to the one found in 
bugzilla (164198).  Would you be willing to add some notes there?  It 
will give you a place to track the progress...

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=164198

  brassow

On Jul 28, 2005, at 2:18 PM, Ming Zhang wrote:

> On Thu, 2005-07-28 at 12:09 -0700, Nathaniel Stahl wrote:
>> We'd like to be able to create a large number of LVs (potentially
>> numbering in the low thousands).  I get failure after LV 226 or so,
>> though - "VG VolGroup01 metadata writing failed".
>>
>> RedHat claims this should be possible with LVM2 on the following web 
>> page:
>>
>> http://www.redhat.com/magazine/009jul05/features/lvm2/
>>
>> I admit to being a little suprised at the 2^32 max LV claim - I was
>> figuring 2^20 as the theoretical max given 2.6's 32 bit device 
>> numbering
>> scheme (20 bits for minor, 12 bits for major).
>>
>> The LVM2 code, at least version 2.00.25 as distributed in FC3, appears
>> to have a check that the minor number is strictly less than 256.
>> Removing this check allows for the creation of working LVs using 
>> minors
>> greater than 256, but LV creation fails with the error "VG VolGroup01
>> metadata writing failed" creating the 227th LV.  Even with the minor
>> limit in place - I can't create more than 226 LVs.
>
> i asked this question before. there is a hard coded limitation in lvm
> metadata, so the real number is like this, limited around 2xx. the
> limitation will be removed in near future. how near? i do not know. :)
>
>
>>
>> Is there a patch that allows this limit to be broken?  Should I be 
>> using
>> a newer version of the tools?  If not currently possible, is this
>> something that will be in the near future?
>>
>> Thanks for any help/advice you can give.
>>
>> -Nate Stahl
>>
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>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
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