Adding Switch to SAN

[Sam Barton]

we recently added two switches to our EMC SAN. the lun's that were previously assigned to our system via a direct conneciton, now show up with a NO_HW message and a new set of of disks (same number and size) appears in ioscan output. the new disks have different HW adresses. so, how do i get the "new" disks to be recognized as the old LUN's?

NOTE: there are very critical oracle DB's living on those LUN's so i am a little aprehensive about doing anything overly intrusive.

currently we have removed the switches and replaced the direct connections and everything came back. any ideas?

[Sundar_7]

Hi,

There are couple of ways you can do it.

1) If the new device files are different from the old one only by the controller number (i.e only CX is different) then you can change the controller instance number.

2) I understand you are not able to activate the volume groups? - I would try a vgscan

# mv /etc/lvmtab /etc/lvmtab.OLD
# vgscan -av

You will have to manipulate the alternate links.

3) Or you can manually export the volume groups and import them with the new physical disks.

Good luck :-)

Sundar.

[Jim Mallett · Accepted solution]

Sam,

A while ago I went through some path changes to my EMC array. I got some great responses and learned a bunch, here's the thread:
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=191717

For me, EMC was kind enough to put together a spreadsheet that illustrated the device path changes before hand so I was able to prepare for it.
Even if they haven't, you should be able to handle this fairly quickly.

Hope the link helps....
Jim

[Sam Barton]

Thanks, to both of you. i will give it a shot next time i can take the sytem down.

Jim- i read your thread and i would bet that you have more experience than me. i will keep you all posted

[Jeff Schussele]

Hi Sam,

The only proper way to do this will involve downtime. Any change to the zoning in a SAN almost always results in new devices. You need to prepare for it by using the EMC utils like syminq to get the LUN IDs for the LUNs you now have & then while down and using the switch again to get the IDs for the new LUNs & then match them up to transistion to the new LUNs.
For instance, you can use
vgexport -m mapfile -spv /dev/vg_name
to get the export file & then vgimport when the switch is in place & the new LUNs are visible
If these are raw - just start using the new devices & rmsf out the old.
But the bottom line is you're not going to ba able to do this on the fly.

Rgds,
Jeff

[Sam Barton]

that was the thought, we gave it out first shot over the weekend, but when we couldnt work out how to get the new paths to be recognized as the old LUN's we rolled it back and decided to ask someone who knows what they are doing (that would be you).