Bug 612399

Event posted on 07-08-2010 05:23am CST by jnomura

Cloning from IT 378094 / BZ 518982 which was about dracut and multipath 
root devices.

NEC's concerns about blacklist methods in RHEL 6:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
multipath.conf can be written in 2 ways:
  1) blacklist everything and add specific devices to blacklist_exceptions
  2) blacklist specific devices

RHEL 5 used method 1, but it appears RHEL 6 is switching to method 2.

Both look same but if you add a local disk to the system after
installation, for example, (2) will result in treating the new disk as a
multipath device, but (1) will not.  The result with (2) would be
confusing for customers, so RHEL5 anaconda took the approach (1).
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Email response from Peter Jones (anaconda engineering):
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Well, he's not entirely correct - we're not using an "empty"
blacklist; we're listing certain classes of things as blacklisted by
default - we're blacklisting all SATA devices, for example, which is
how local disks will typically be attached.

That being said, it really would be better if /sbin/multipath didn't
try to create multipath devices when there's only one path, but
that's an issue for the multipath maintainers, not for the installer.

I would be happy to accept a patch to anaconda to create a
multipath.conf at the _end_ of installation which creates
blacklist_exceptions entries for each identified multipath device
and makes a generic blacklist for everything else, though it's of
questionable benefit given the blacklisting of classes of devices
I mentioned above. It's impractical to use this method of operation,
though. 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


See attached patch from NEC: 
anaconda-use-blacklist_exceptions-rhel6snap6.patch 
This event sent from IssueTracker by dwu  [Support Engineering Group]
 issue 1113383

Created attachment 430245 [details]
/tmp/anaconda-use-blacklist_exceptions-rhel6snap6.patch

Should be fixed in anaconda-13.21.59-1 .

[root@dhcp70-190 ~]# multipath -ll
mpatha (3600a0b800034867a000005cd47d96f66) dm-0 SGI,IS400
size=339G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=6 status=active
| `- 1:0:0:3 sdb 8:16 active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  `- 0:0:0:3 sda 8:0  active ghost running

/etc/multipath.conf contains:
[root@dhcp70-190 ~]# cat /etc/multipath.conf 
# multipath.conf written by anaconda

defaults {
        user_friendly_names yes
}
blacklist {
        devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
        devnode "^hd[a-z]"
        devnode "^dcssblk[0-9]*"
        device {

<SKIPPED>

blacklist_exceptions {
        wwid 3600a0b800034867a000005cd47d96f66
}
multipaths {
        multipath {
                uid 0
                alias mpatha
                gid 0
                wwid 3600a0b800034867a000005cd47d96f66
                mode 0600
        }
}

Tested on build RHEL6.0-20100811.2 / x86_64 with anaconda-13.21.74-1.el6.
Moving to VERIFIED.

Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.