Re: ASM bug?
- From: Stefan Koehler <contact@xxxxxxxx>
- To: "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 2 Oct 2014 20:47:40 +0200 (CEST)
Hi Maureen,
thanks for clarification. Unfortunately my Oracle RAC 12.1.0.2 lab is running
with udev, so i have no ASMLIB right here to trace, debug or verify.
However a few things to consider regarding your described ASMLIB behavior:
* DM devices got different major(253)/minor(X) numbers than the underlying path
(e.g. 67/<X>, 68/<X>) - for more details check this documentation (
http://www.lanana.org/docs/device-list/devices-2.6+.txt ). It is much more
likely that the major/minor device number for the path changes due to
failed/deleted/added path. This should be no big issue as well, if you keep
using the multi path bindings (= dm devices) in the right ASMLIB scan
order. However if you flush the whole unused device map (including dm devices),
the kernel assigns the next available major/minor pair for the device
type by next (scsi-)rescan. If you have not changed the "device publishing
order" (e.g. SAN admin can control that to a specific level) in the
meantime it should be no issue as well. However there is some risk for sure (by
LUN changes in the meantime), but i can not think about a valid reason
to flush the whole unused device map (-F) instead of some specific ones due to
a wanted disk change / redesign (-f). Maybe just an unwanted typo.
* Based on your described behavior it seems like ASMLIB does not grab net link
socket messages (e.g. NETLINK_KOBJECT_UEVENT) from linux kernel
properly (= bug) or not at all (= not implemented) like udev does and does not
assign the corresponding new device numbers. You can do stack tracing /
sampling to figure it out.
As this is a new RAC system you may want to consider udev instead of ASMLIB. It
removes a separate (possibly buggy) software layer, but this whole
thing is more like a "religious battle":
http://ardentperf.com/2008/10/08/asmlib-performance-vs-udev/
Best Regards
Stefan Koehler
Oracle performance consultant and researcher
http://www.soocs.de
> Maureen English <maureen.english@xxxxxxxxxx> hat am 2. Oktober 2014 um 18:55
> geschrieben:
>
> Stefan, Andew;
>
> Yes, we are using ASMLIB.
>
> - Maureen
>
>
>
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