[linux-lvm] "System ID" entry missing in metadata (LVM2) ?!

[linux-lvm] "System ID" entry missing in metadata (LVM2) ?!

[Andreas Octav]

Hi again,

It seems that my Volume Groups are missing the "System ID" entry. Is
this a known bug in my version? (lvm2-2.01.14-3.6)
So all nodes have full access to the VG. Does not seem correct to me ...


Best regards,
Andreas Octav

Am Mi 18.10.2006 12:28 schrieb Andreas Octav <Andreas.Octav@anykey.de>:

> Hi,
> 
> i´m new to LVM2 and wondering if it´s possible to restrict access to a
> Volume Group to a single server (e.g. like under vxvm (vxdg
> import/deport)).
> If I import a VG by using vgimport it is still possible to access the
> VG
> on another node in a shared SAN environment. Can I prevent this
> somehow?
> 
> I´m using lvm2-2.01.14-3.6 on servers running SuSE SLES9 SP3 x86_64.
> 
> Kind regards,
> Andreas Octav
> Consultant
> 
> anykey GmbH
> Koenigswinterer Strasse 418
> D-53227 Bonn
> http://www.anykey.de
> 	



Andreas Octav
Consultant

anykey GmbH
Koenigswinterer Strasse 418
D-53227 Bonn
http://www.anykey.de
	

Re: [linux-lvm] "System ID" entry missing in metadata (LVM2) ?!

[Jonathan E Brassow]

>> Hi,
>>
>> i�m new to LVM2 and wondering if it�s possible to restrict access to a
>> Volume Group to a single server (e.g. like under vxvm (vxdg
>> import/deport)).
>> If I import a VG by using vgimport it is still possible to access the
>> VG
>> on another node in a shared SAN environment. Can I prevent this
>> somehow?
>>
>> I�m using lvm2-2.01.14-3.6 on servers running SuSE SLES9 SP3 x86_64.
>>

You can use tags to achieve this, or you can specify specific volume 
groups and logical volumes in lvm.conf under "volume_list".

  brassow

Re: [linux-lvm] "System ID" entry missing in metadata (LVM2) ?!

[Andreas Octav]

Hi,

thanks for your response Jonathan, but I want to share the VGs between 
the hosts. So I hoped that there is something like this functionality:
-> "vgimport VG" writes some kind of hostid (system_id?) in the metadata
-> other hosts can�t access the VG
-> "vgdeport VG" removes the ID, so anyone else can import the VG

My C knowledge isn�t very good, but the sources seem to include a 
functionality like the one mentioned above.


Kind regards,
Andreas

Jonathan E Brassow schrieb:
>
>>> Hi,
>>>
>>> i�m new to LVM2 and wondering if it�s possible to restrict access to a
>>> Volume Group to a single server (e.g. like under vxvm (vxdg
>>> import/deport)).
>>> If I import a VG by using vgimport it is still possible to access the
>>> VG
>>> on another node in a shared SAN environment. Can I prevent this
>>> somehow?
>>>
>>> I�m using lvm2-2.01.14-3.6 on servers running SuSE SLES9 SP3 x86_64.
>>>
>
> You can use tags to achieve this, or you can specify specific volume 
> groups and logical volumes in lvm.conf under "volume_list".
>
>  brassow
>
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

Re: [linux-lvm] "System ID" entry missing in metadata (LVM2) ?!

[Jonathan E Brassow]

I think it works in the reverse...

vgexport adds a generic tag to the volume groups metadata, basically 
saying "ignore me".  Doing a 'vgs' on an exported volume group shows 
the 'x' attribute; and trying to activate that volume group results in 
"Volume group "<vgname>" is exported".  So, after performing this 
operation, no-one can use the volume group (until vgimport is run).

vgimport removes the generic tag, allowing the VG to be activated and 
used again.  One this command is run, anyone that can see the volume 
group can use/alter the volume group.

Think of it as "import/export from the set of usable volume groups".

If you want to share the VGs, you have two options:
1) Use clustered LVM2.  This is really the best option.
2) Set up your logical volumes on one machine (you should only use 
linear or stripe in this scenario - never mirror or snapshot).  Never 
change the logical volume layout after creating it unless the other 
hosts have deactivated the volume groups being  shared.  Run 'vgchange 
-ay' on all machines that have access to the devices.

Clustered LVM2 makes sure that all changes to a shared volume group are 
serialized to prevent corruption and makes sure to activate/deactivate 
volumes on a cluster-wide basis.   If you are never going to change 
anything (no risk of corruption or inconsistencies), you might be able 
to get away with using LVM2 as it is.

If you need more specialized access, you can use tags.

Note, if you are sharing a logical volume, the application (or file 
system) sharing that volume must be cluster-aware.

  brassow

On Oct 18, 2006, at 11:02 AM, Andreas Octav wrote:

> Hi,
>
> thanks for your response Jonathan, but I want to share the VGs between 
> the hosts. So I hoped that there is something like this functionality:
> -> "vgimport VG" writes some kind of hostid (system_id?) in the 
> metadata
> -> other hosts can�t access the VG
> -> "vgdeport VG" removes the ID, so anyone else can import the VG
>
> My C knowledge isn�t very good, but the sources seem to include a 
> functionality like the one mentioned above.
>
>
> Kind regards,
> Andreas
>
> Jonathan E Brassow schrieb:
>>
>>>> Hi,
>>>>
>>>> i�m new to LVM2 and wondering if it�s possible to restrict access 
>>>> to a
>>>> Volume Group to a single server (e.g. like under vxvm (vxdg
>>>> import/deport)).
>>>> If I import a VG by using vgimport it is still possible to access 
>>>> the
>>>> VG
>>>> on another node in a shared SAN environment. Can I prevent this
>>>> somehow?
>>>>
>>>> I�m using lvm2-2.01.14-3.6 on servers running SuSE SLES9 SP3 x86_64.
>>>>
>>
>> You can use tags to achieve this, or you can specify specific volume 
>> groups and logical volumes in lvm.conf under "volume_list".
>>
>>  brassow
>>
>>
>> _______________________________________________
>> linux-lvm mailing list
>> linux-lvm@redhat.com
>> https://www.redhat.com/mailman/listinfo/linux-lvm
>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>>
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

Re: [linux-lvm] "System ID" entry missing in metadata (LVM2) ?!

[Andreas Octav]

Sorry, i did not express myself correct: I do not want to share the 
logical volumes for the use of a Cluster Filesystem (OCFS etc.). I just 
want to be able to switch the volume groups from one host to another, so 
only one host at a time has access to a specific volume group. But if I 
do an vgimport on a host, every host that sees the VG can use it...
I am going to install several Oracle/SAP instances in different Volume 
Groups and I want to be sure that only one host can access a specific VG 
at a time.
The Veritas Volume Manager for example automatically sets a host id of 
the system that imports a VG (DiskGroup in Veritas terms) during an 
import, so any other system has to "force" an import, resulting in a 
loss of access on the former owner.

Btw: In LVM1 the system ID is used:
..snip..

vgdisplay  VG Name               vg
vgdisplay  System ID             PV_IMPKnoppix1077635774
vgdisplay  Format                lvm1
..snap..

Is this obsolete in LVM2?


Jonathan E Brassow schrieb:
> I think it works in the reverse...
>
> vgexport adds a generic tag to the volume groups metadata, basically 
> saying "ignore me".  Doing a 'vgs' on an exported volume group shows 
> the 'x' attribute; and trying to activate that volume group results in 
> "Volume group "<vgname>" is exported".  So, after performing this 
> operation, no-one can use the volume group (until vgimport is run).
>
> vgimport removes the generic tag, allowing the VG to be activated and 
> used again.  One this command is run, anyone that can see the volume 
> group can use/alter the volume group.
>
> Think of it as "import/export from the set of usable volume groups".
>
> If you want to share the VGs, you have two options:
> 1) Use clustered LVM2.  This is really the best option.
> 2) Set up your logical volumes on one machine (you should only use 
> linear or stripe in this scenario - never mirror or snapshot).  Never 
> change the logical volume layout after creating it unless the other 
> hosts have deactivated the volume groups being  shared.  Run 'vgchange 
> -ay' on all machines that have access to the devices.
>
> Clustered LVM2 makes sure that all changes to a shared volume group 
> are serialized to prevent corruption and makes sure to 
> activate/deactivate volumes on a cluster-wide basis.   If you are 
> never going to change anything (no risk of corruption or 
> inconsistencies), you might be able to get away with using LVM2 as it is.
>
> If you need more specialized access, you can use tags.
>
> Note, if you are sharing a logical volume, the application (or file 
> system) sharing that volume must be cluster-aware.
>
>  brassow
>
> On Oct 18, 2006, at 11:02 AM, Andreas Octav wrote:
>
>> Hi,
>>
>> thanks for your response Jonathan, but I want to share the VGs 
>> between the hosts. So I hoped that there is something like this 
>> functionality:
>> -> "vgimport VG" writes some kind of hostid (system_id?) in the metadata
>> -> other hosts can�t access the VG
>> -> "vgdeport VG" removes the ID, so anyone else can import the VG
>>
>> My C knowledge isn�t very good, but the sources seem to include a 
>> functionality like the one mentioned above.
>>
>>
>> Kind regards,
>> Andreas
>>
>> Jonathan E Brassow schrieb:
>>>
>>>>> Hi,
>>>>>
>>>>> i�m new to LVM2 and wondering if it�s possible to restrict access 
>>>>> to a
>>>>> Volume Group to a single server (e.g. like under vxvm (vxdg
>>>>> import/deport)).
>>>>> If I import a VG by using vgimport it is still possible to access the
>>>>> VG
>>>>> on another node in a shared SAN environment. Can I prevent this
>>>>> somehow?
>>>>>
>>>>> I�m using lvm2-2.01.14-3.6 on servers running SuSE SLES9 SP3 x86_64.
>>>>>
>>>
>>> You can use tags to achieve this, or you can specify specific volume 
>>> groups and logical volumes in lvm.conf under "volume_list".
>>>
>>>  brassow
>>>
>>>
>>> _______________________________________________
>>> linux-lvm mailing list
>>> linux-lvm@redhat.com
>>> https://www.redhat.com/mailman/listinfo/linux-lvm
>>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>>>
>>
>> _______________________________________________
>> linux-lvm mailing list
>> linux-lvm@redhat.com
>> https://www.redhat.com/mailman/listinfo/linux-lvm
>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>>
>
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

Re: [linux-lvm] "System ID" entry missing in metadata (LVM2) ?!

[Alasdair G Kergon]

Try setting hosttags - see man lvm.conf.

lvchange --addtag host1 vg1/lv1
lvchange -ay vg1/lv1

lvchange -an vg1/lv1
lvchange --addtag host2 vg1/lv1
lvchange -ay vg1/lv1

Alasdair
-- 
agk@redhat.com