[linux-lvm] Volume groups on SAN storage

[linux-lvm] Volume groups on SAN storage

[Thomas Meller]

Hello everybody,

recently (today) I had a problem.

I'm trying to create a HA Cluster for a DCE server.
This is difficult work and sometimes very confusing.

My goal is to make it bootable from a SAN.
So far I managed to install GRUB and boot the machine. The rootfs and the rest can be
mounted.
I found, then, that the SCSI-devices inside one of my volume groups were the wrong ones.

What is special about that is that the same content on a device can be seen on different
SCSI-devices. This is due to some mirroring within the storage sytems. I cannot avoid that.

Now, I have a readonly physical volume inside one of my volume groups. I want to insert the
writeable mirror and get rid of the readonly.
AFAICS this is not possible because I cannot force vgscan to insert a specified SCSI-device.
Of course the VGDA is marked "part of VG xxx" and cannot be written anymore. So it cannot be
imported nor exported or added to a new VG.

Maybe there is an option anywhere how to scan a particular device. 

Does anybody know how to trick LVM?
Is there a hexeditor to patch the VGDA backups to use different /dev/sdXX devices?
And if so, does that help?

I'm using redhat 8.0 and I'm bound to that version.

TIA

Thomas

-- 
Thomas Meller
mailto: thomas.meller@t-systems.ch
mailto: thomas.meller@gmx.net
----
...Our continuing mission: To seek out knowledge of C, to explore strange
UNIX commands, and to boldly code where no one has had a man page before.

Re: [linux-lvm] Volume groups on SAN storage

[Heinz Mauelshagen]

Thomas,

sounds odd that your storage system exposes more than one device
to access the same data.

Anyway: the only way to avoid accesses to SCSI devices you don't want to be used
by LVM1 is to move their device nodes out of /dev
(eg, mkdir /dev/.SAV; mv /dev/sdc2 to /dev/.SAV) and rerun vgscan afterwards.

FYI: with LVM2, youd can set up device name filters to avoid accesses
     to devices.

Regards,
Heinz    -- The LVM Guy --


On Fri, Feb 13, 2004 at 03:06:14PM +0100, Thomas Meller wrote:
> Hello everybody,
> 
> recently (today) I had a problem.
> 
> I'm trying to create a HA Cluster for a DCE server.
> This is difficult work and sometimes very confusing.
> 
> My goal is to make it bootable from a SAN.
> So far I managed to install GRUB and boot the machine. The rootfs and the rest can be
> mounted.
> I found, then, that the SCSI-devices inside one of my volume groups were the wrong ones.
> 
> What is special about that is that the same content on a device can be seen on different
> SCSI-devices. This is due to some mirroring within the storage sytems. I cannot avoid that.
> 
> Now, I have a readonly physical volume inside one of my volume groups. I want to insert the
> writeable mirror and get rid of the readonly.
> AFAICS this is not possible because I cannot force vgscan to insert a specified SCSI-device.
> Of course the VGDA is marked "part of VG xxx" and cannot be written anymore. So it cannot be
> imported nor exported or added to a new VG.
> 
> Maybe there is an option anywhere how to scan a particular device. 
> 
> Does anybody know how to trick LVM?
> Is there a hexeditor to patch the VGDA backups to use different /dev/sdXX devices?
> And if so, does that help?
> 
> I'm using redhat 8.0 and I'm bound to that version.
> 
> TIA
> 
> Thomas
> 
> -- 
> Thomas Meller
> mailto: thomas.meller@t-systems.ch
> mailto: thomas.meller@gmx.net
> ----
> ...Our continuing mission: To seek out knowledge of C, to explore strange
> UNIX commands, and to boldly code where no one has had a man page before.
> 
> _______________________________________________
> 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/

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

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Heinz Mauelshagen                                 Red Hat, Inc.
Consulting Development Engineer                   Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen@RedHat.com                            +49 2626 141200
                                                       FAX 924446
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