Re: ASM over SLVM

From the HP-UX 10g Oracle RAC and clusterware install guide, page 105 of the pdf version, last bullet point in the page:

1) Although you can specify a logical volume as a device in an Automatic Storage Management disk group, Oracle does not recommend their use......
.
From the same guide on page 104, 4th point:

2) For each disk that you want to add to a disk group, enter the following command
on any node to verify that it is not already part of an LVM volume group:
# /sbin/pvdisplay /dev/dsk/cxtydz
If this command displays volume group information, the disk is already part of a
volume group. The disks that you choose must not be part of an LVM volume
group.

Does this , at least the last point, 2) not seem contradictory, from what the hp docs say?

----- Original Message ----
From: Kevin Closson <kevinc@polyserve.com>
To: oracle-l@freelists.org
Sent: Thursday, 28 December, 2006 11:19:31 PM
Subject: RE: ASM over SLVM

 
Naqi sent me the HP doc. It says that ASM->SLVM is for multi-pathing,
global
device naming and external-write protection... three of the reasons
people
deploy RAC on PolyServe in the Linux world btw...

I have seen that Oracle is starting to admit this necessity in other
technology stacks as well such as VxVM with Sol or AIX.
 

 
 The main reason for this requirement is to expedite ASM support with
SGeRAC. We leverage existing
HP-UX capabilities to provide multipathing for SLVM logical volumes,
using either the PV Links feature,
or separate products such as HP StorageWorks Secure Path that provide
multipathing for specific
types of disk arrays. Other advantages of the "ASM-over-SLVM"
configuration are as follows:
* ASM-over-SLVM ensures that the HP-UX devices used for disk group
members will have the
same names (the names of logical volumes in SLVM volume groups) on all
nodes, easing
ASM configuration.
* ASM-over-SLVM protects ASM data against inadvertent overwrites from
nodes inside/outside
the cluster. If the ASM disk group members are raw disks, there is no
protection currently
preventing these disks from being incorporated into LVM or VxVM
volume/disk groups.
 
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