[linux-lvm] Devices seen twice - how does LVM handle ?

[Markus Baertschi]

Rainer,

I'm using fiber cards coming with a load-balancing driver and a SAN-Storage
box (IBM FastT 700) box. Unfortunately the storage-controlles got reconfigured
to accommodate more devices on other ports. This broke the configuration for me.
As it happens I found out a couple of months later when the new devices were
in production (We reboot out servers only when necessary). I can not fix the
configuration immediately and am trying to find out how to survive best
until I can fix the real problem it.

At the moment I'm pulling a fiber to have only one path as the installed LVM
version (0.9beta ?) just crashes if is sees two devices pointing to the 
same disk.
The most recent version (1.0.7) does not have this problem. It allows me
the keep both fibers connected. But I don't know how it handles this situation
and started this discussion to find out.

Markus


>It did not follow this discussion right from the start, so I might have mis=
>sed=20
>something...

>We are running 3 fileservers with raid devices attached by fibrechannel. Si=
>nce=20
>each divice can be reached by 2 seperate io paths we are using a multipath=
>=20
>setup based on the md interface (on top of the multipath md devices we=20
>finally run a software mirror (raid1)). This works just fine for our server=
>s=20
>(running suse8.2) .  At the beginning we also had trouble with lvm1 since i=
>t=20
>was able to see the volume on different levels of abstraction: lvm scanned=
>=20
>the real disks, it also scanned the md multipath metadevice and this probab=
>ly=20
>led to the bad behaviour that whenever creating new logical volumes the=20
>complete configuration was invalid and so all data lost.=20

>We then changed to lvm2 since it has the ability to specify which devices t=
>o=20
>scan for lvm metadata and since then everything works fine. =20

>Rainer



--
  Markus Baertschi             Phone: ++41 (21) 807 1677
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