[rhelv6-list] LVM question about filter option in lvm.conf file and persistent disk name format

[george application]

Hi,

Let me describe an strange issue that I had before a month to a customer.

I had two disks with two paths per disk and I wanted to create a LVM volume
on both of them (different volume and
diffente volume group).
So, I had to edit the lvm.conf file to add on the FILTER option the disks
that volume manager will scan for volumes. In my configuration I had an
internal disk (sda which had the root & swap logical volumes) and two
external (storage) disks with two paths per disk: external disk 1 (mpath0)
paths: sdb sdc external disk2 (mpath1) paths: sdd sde For the external
disks I had enabled the multipathd and I had mpath0 for sdb,sdc and mpath1
for sdd, sde. Suddenly, my internal disk sda changed to sdc. I checked it
by the pvscan command. And the sdc path changed to sda. That time, I had
the default FILTER option enabled on lvm.conf. I guess that this was the
reason that I didn't lose my root volume which I had on internal disk. Also
I didn't had any volumes on mpath0 and mpath1. Finally, after a reboot, my
internal disk name switched back to the initial name (sda). I believe that
I have to change the default filter option: filter = [ "a/.*/" ] to filter
= [ "a|/dev/sda|", "a|/dev/mapper/mpath.*|" ] which means that volume
manager will scan the /dev/sda and /dev/mapper/mpath* for LVM volumes. Also
I would like to notice that with the filter = [ "a|/dev/sda|",
"a|/dev/mapper/mpath.*|" ] I will not have any "found duplicate pv"
warnings, on pvscan execution command. If I change the default filter
option to [ "a|/dev/sda|", "a|/dev/mapper/mpath.*|" ], then what will
happen to my logical volumes in the future if suddenly the sda became sdc
again? In this condition first of all I will loose my root disk. I don't
know if I will have any other consequences on the volumes on my mpath*
devices. My question is what persistent disk name I can use instead of
/dev/sda on filter option of lvm.conf file, because if the sda became sdc
then I will have problems with my logical volumes.


Regards,
George

2012/8/21 george application <applicgs at gmail.com>

> Hi,
>
> Does anyone know if I can use the disk name /dev/disk/by-id/scsi-xxxx
> format on the FILTER option of lvm.conf file instead of /dev/sdX?
>
> For example, I don't want to use the disk name "/dev/sda", because it is
> not persistent, and some times my sda changes to sdc.
>
> Thanks in advance,
> AGS
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