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For those of you who aren’t nerds ignore this. I wanted to put up a note that could be found via a web search on an issue we had here at work.One that even the IBM GPFS support guys were scratching their heads over.

When using dm multipath on linux and then mounting gpfs filesystems you MUST make a modification to the /etc/mmfs/etc/nsddevices file. Either modify the existing file or copy the sample file from /usr/lpp/mmfs/samples/nsddevices.sample to /etc/mmfs/etc/nsddevices.

The modification that must be made is to change the linux section of the file to

if [[ $osName = Linux ]]
$awk ‘                                                          \
/dm-/   { if (NF > 3 && $3 > 1) print $4 ” dm-mpio” ; next }  \
‘ /proc/partitions 2>$STDERR

and uncomment the return part of the following section

# To bypass the GPFS disk discovery (/usr/lpp/mmfs/bin/mmdevdiscover),
return 0

The reason that you have to do this is that the dm multipath functionality of linux creates a device /dev/dm-# and gpfs will not automagically look for this. It looks for sd* and hd* devices only. (well emcpower and vpath also to be picky). That and it uses the wrong device type of “generic” instead of “dm-mpio” Without both of these, finding the right device, and using the write driver type, gpfs will not work correctly.

For those interested gpfs uses the script mmdevdiscover to find usable devices with which to build NSD’s on. Here is the subsection of the script that does this functionality for Linux

elif [[ $osName = Linux ]]
# Get the names of all disks, vpaths, etc.
$awk ‘                                                                 \
/emcpower/   { if (NF > 3 && $3 > 1) print $4 ” powerdisk” ; next }  \
/vpath/      { if (NF > 3 && $3 > 1) print $4 ” vpath”     ; next }  \
/[sh]d/      { if (NF > 3 && $3 > 1) print $4 ” generic”   ; next }  \
‘ /proc/partitions 2>$STDERR

Using the /var/mmfs/etc/nsddevices file modifies the way gpfs will discover the necessary devices and will thus find the /dev/dm-# devices. I imagine you could also just modify the /usr/lpp/mmfs/bin/mmdevdiscover file directly, but if you do this BEWARE any gpfs upgrades my overwrite the file without you knowing it until your file systems go away. It’s much safer to just modifiy the nsddevices file and call it good.

Enough said. Good luck and may the force be with you. (-:

I’m going to sound like an old fogey with this one, I just know it. Schools today are not the same as when I went to school. I guess they just taught differently before the age of computers.

The reason for this post is that in this months newsletter from the school I saw some interesting tidbits

  • Due to last year’s high test scores, Pacific Grove Middle School qualified to apply for the California Distinguished School Award.
  • Principal to my wife. “We don’t like to treat the children as individuals here.” (My own quote from a phone conversation with the principal about Megan’s transcripts from Scotland)
  • Some students have been bringing rubber bands to school and shooting pieces of paper during class. This is an illegal activity and will result in detention if a student is caught.
  • –refraining from any public displays of affection. This rule is absolute so we do not allow hugging, kissing, hand holding or any other displays of affection on campus at any time.
  • Students are reminded not to chew gum at any time
  • They need to earn 16 hours of community service. Eight of these hours must be earned during the 8 grade.

I just found these tidbits interesting on a Monday morning.

Believe it or not I am seriously considering a new career. And yes, it’s in a different state. So much for not moving for 5+ years.

If all goes as we think it might, I would finish off a year or two here at Fleet before moving on. So, this isn’t a sudden jump up and go kind of thing. We’ll have plenty of time to work through the good and bad. Make some plans and do it in a more coordinated fashion.

I never thought I would leave the computer field, but the longer I do it the less excitement and challenge it is and the more work it becomes. The fun is pretty much faded at this point. If you think I’m crazy, you try working at a government facility for a while. So, when this opportunity was put before me I didn’t immediately say no. I said I’d think about it.

Now the more we talk about it, the more viable it seems. Just because I’ve made a career out of supercomputers, and it pays pretty well. It doesn’t mean I can’t change. Things are really in the vapor phase at this point, but it’s possible that things could harden into reality.

A partner/co-owner in a 30 year old business. It has peaked my interest.

Where’s the fortune cookie when you need it?

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March 2009
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