drbd-user March 2010 archive
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drbd-user: Re: [DRBD-user] Detection of Logical Volume on nested

Re: [DRBD-user] Detection of Logical Volume on nested LVM

From: Olivier LAMBERT <lambert.olivier_at_nospam>
Date: Tue Mar 09 2010 - 10:39:34 GMT
To: drbd-user@lists.linbit.com

Hmmm. I like riddles, so I'm going to google this. Is there any simple
solutions, in example force drbd to deal with that ?

Regards,

Olivier
XO Project
http://xen-orchestra.com

On Tue, Mar 9, 2010 at 11:22 AM, Lars Ellenberg
<lars.ellenberg@linbit.com> wrote:
> On Tue, Mar 09, 2010 at 10:59:54AM +0100, Olivier LAMBERT wrote:
>> I've got your point. I know my first message is long and maybe
>> complicated. It seems you "jump" some lines. It's not "nested" LVM as
>> described in the doc (because I RTFM before try to ask help).
>>
>> My problem is not located on DRBD hosts. I've run some test, and I can
>> really simplify the example. Please, read this, I think it's clear now
>> :
>> Let's say I export a simple physical volume with DRBD. So, NO LVM in
>> DRBD, just replicate "/dev/sdb" for example, and export it
>> (/dev/drbd0) on each DRBD host with iSCSI.
>>
>> So, on ALL my clients (connected iSCSI), I saw with "fdisk -l" :
>> Disk /dev/sdb: 2998.8 GB, 2998869356544 bytes
>>
>> So, my CLIENT1 connected to DRBD1, decide to create a volume group and
>> a logical volume.
>> Despite all my efforts (vgscan, pvscan, lvscan), CLIENT2 connected to
>> replicated DRBD2, cannot see anything ! No VG, no LV ! Nothing !
>>
>> But, if I decide to do that on DRBD2 :
>> drbdadm disconnect ressource && drbdadm connect ressource
>>
>> Just after THIS, I can see all the stuff I've created on CLIENT1.
>>
>> So, it's NOT a question of LVM on DRBD, because in this case, I don't
>> use it anymore. I can undestand if LVM data's on client are not
>> replicated on each DRBD hosts, but WHY it works if I
>> disconnect/reconnect these two ? It doesn't have any sense to me....
>
> Does the keyword "cache coherence" help?
>
> --
> : Lars Ellenberg
> : LINBIT | Your Way to High Availability
> : DRBD/HA support and consulting http://www.linbit.com
>
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