Re: [linux-lvm] disk naming

[Matt Schillinger <mschilli@vss.fsi.com>]

If i'm NOT using devfs, can i reliably (assuming that disks are on the
same scsi id/lun/host channel) use lvm?

Scenario:

LV is created with device /dev/sdd, which is on host channel 2

Machine is shutdown, and a new raid is connected on host channel 1, with
one disk.

Machine is restarted, and the 1 disk on the host channel 1 raid takes
/dev/sdd. The original disk is now /dev/sde.

Will LVM find the correct disk?

Matt Schillinger
mschilli@vss.fsi.com



On Fri, 2003-01-03 at 10:46, Goetz Bock wrote:
> 
> On Fri, Jan 03 '03 at 10:08, Matt Schillinger wrote:
> > this should be a simple question, but I can't find a direct discussion
> > in the lvm documentation. I believe that i have found that LVM will find
> > appropriate PV's regardless of their name (sda,sdb).. Is this true?
> Kind of. When you created (maybe even just used) a PV/VG with DEVFS it
> will only work with devfs. 
> IIRC when you compile DEVFS into the kernel, but do not mount it, you
> can create PVs, but createvg will not find them unless you mount devfs.
> 
> > Do i need devfs to ensure that i always have the same disk naming, or
> > will LVM handle this for me?
> devfs does not ensure you have the same names.
> 
> > I am currently using scsidev for naming purposes, but have found that
> > vgcreate will not work with scsidev device names
> > (/dev/scsi/sdh0-0c0i4l2p1)
> > /dev/scsi/sd(host=0,scsiid=4,LUN=2,partition #=1)
> Most likely the userspace tools do not search the /dev/scsi/sdxxx
> devices for PV signatrue. IIRC there is one file where you can add them. 
> It's in tools/lib/lvm_check_partitioned_dev.c but I've no idea how to
> add your devices.
> -- 
> Goetz Bock       (c) 2002 as     blacknet.de - Munich - Germany   /"\
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-- 
Matt Schillinger
System Administrator
FlightSafety International
mschilli@vss.fsi.com
314-551-8403