Volume groups on SAN storage

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: [email protected]
mailto: [email protected]
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...Our continuing mission: To seek out knowledge of C, to explore strange
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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 --

*** 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
[email protected] +49 2626 141200

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