[linux-lvm] Problem of LVM on Suse

[linux-lvm] Problem of LVM on Suse

[adimaths]

Hi, 

I am facing a problem in using LVM bundled with Suse Enterprise server 8 
,connected to storage area newtork
System configuration:
A storage area network is connected to a server with OS Suse Enterprise 
server 8.
So there are multiple scsi devices whose physical disk is identical. 

We are creating a Pseudo device file asscociated with identical scsi devices 
using a driver that we have created.
eg : /dev/pseudo-device -> /dev/sda , /dev/sdb 

Now using the bundled LVM on such pseudo device is a problem.
problem details:
pvcreate /dev/pseudo-device
[result] ok. 

pvscan
[result] it shows the scsi device associated with this pseudo device ie 
/dev/sda and not our pseudo device. 

If LVM bypasses our pseudo device then the purpose of creating this device 
and associating it with scsi is futile. 

The irony is, LVM works fine on RH 2.1 kernel = 2.4.9-e.3 and also with RH 
7.2
However the above mention problem is observed on Suse Enterprise server 8 
,RH 2.1 kernel =2.4.9-e.25, RH 7.3 and RH 8.0. 

Would request you to clarify the following :
1>Could you please tell me how this problem can be rectified ? 

2>Is it that Lvm that is bundled with the OS can't be used for
the above mentioned purpose ? 

3>If it can't be , then what design feature
of the current LVM prevents it from supporting the above task? 

4> Can any change in our product help us to solve this problem? 

5>Moreover I think LVM on RedHat is working just by chance.
I think pvscan depends on the order of the devices in the
/proc/partitions , and hence when our pseudo devices are
at the end of the /proc/paritions , pvscan shows our devices
as active else it shows scsi as active. 

Is my inference correct? 

Regards
Aditya Vasudevan 

[linux-lvm] Re: Problem of LVM on Suse

[Heinz J . Mauelshagen]

On Thu, Oct 23, 2003 at 06:50:29PM -0600, adimaths@softhome.net wrote:
> Hi, 
> 
> I am facing a problem in using LVM bundled with Suse Enterprise server 8 
> ,connected to storage area newtork
> System configuration:
> A storage area network is connected to a server with OS Suse Enterprise 
> server 8.
> So there are multiple scsi devices whose physical disk is identical. 
> 
> We are creating a Pseudo device file asscociated with identical scsi devices 
> using a driver that we have created.
> eg : /dev/pseudo-device -> /dev/sda , /dev/sdb 
> 
> Now using the bundled LVM on such pseudo device is a problem.
> problem details:
> pvcreate /dev/pseudo-device
> [result] ok. 
> 
> pvscan
> [result] it shows the scsi device associated with this pseudo device ie 
> /dev/sda and not our pseudo device. 
> 
> If LVM bypasses our pseudo device then the purpose of creating this device 
> and associating it with scsi is futile. 
> 
> The irony is, LVM works fine on RH 2.1 kernel = 2.4.9-e.3 and also with RH 
> 7.2
> However the above mention problem is observed on Suse Enterprise server 8 
> ,RH 2.1 kernel =2.4.9-e.25, RH 7.3 and RH 8.0. 
> 
> Would request you to clarify the following :
> 1>Could you please tell me how this problem can be rectified ? 

Change the sort-order (as you suggested below)

> 
> 2>Is it that Lvm that is bundled with the OS can't be used for
> the above mentioned purpose ? 
> 
> 3>If it can't be , then what design feature
> of the current LVM prevents it from supporting the above task? 
> 
> 4> Can any change in our product help us to solve this problem? 
> 
> 5>Moreover I think LVM on RedHat is working just by chance.
> I think pvscan depends on the order of the devices in the
> /proc/partitions , and hence when our pseudo devices are
> at the end of the /proc/paritions , pvscan shows our devices
> as active else it shows scsi as active. 
> 
> Is my inference correct? 

Yes.

LVM2 is much more suitable to cover such vendor-specific configurations,
because it has configurable device name filters. LVM1 needs code changes
to support additional device name spaces.

> 
> Regards
> Aditya Vasudevan 

-- 

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
                                                       FAX 924446
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