AIX 5.3 and Oracle RAC ASM diskmanagement
- From: erikw_nl@xxxxxxxxx
- Date: 20 Apr 2006 23:48:22 -0700
Hi,
We are using Oracle/RAC 10GR2 with ASM for disk management of diskspace
used by the database. ASM requires that the disks are NOT included in a
volume group and also uses the first block of the disk to store
essential information. RAC 10GR2 does not need HACMP anymore.
This setup imposes a serious problem for AIX systemmanagement:
1) It is difficult to distinguish disks on the AIX servers since they
are not part of a volume group.
2) The usage of the first block by Oracle implies that chdev may not be
used to create a PVID, since chdev overwrites the first block. If chdev
is being used on a ASM disk, Oracle can not read that disk, and the
database is lost.
3) Since ASM disks are writable by all servers in the cluster,
reserve_policy is switched off, the probability that a disk is by
accident used for a volume group is not unthinkable, with fatal
consequences for the database.
4) Changes in SAN configuration may imply that existing devices have to
be rearranged with rmdev. Rmdev removes disk devices and other devices
nodes in /dev having equal major/minor number. Using sybolic names for
hdisk devices in the Oracle database by creating devices nodes in /dev
is not a viable option.
In my opion these are some serious integration issues between Oracle
ASM and AIX. When my DBA collegues reported this to Oracle via a TAR
Oracle commented: "Works as designed, AIX system management should not
worry about PVID's and never give PVID to disks which are being used in
a database. Oracle will find out itself how disks should be used."
The way ASM handles AIX disks is not acceptable for our AIX system
managers, and we are looking for way to set things up in such a way so
that risks are reduced.
Question: Does anybody have any clues for solving this problem, are
there ways to reduce probability on mistakes (using ASM disk to make
volume group). How can we find out where disks are used.
Thanks in advance.
Erik
.
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