Today I got a request to expand an existing LUN on a CLARiiON that is presented to an existing RHEL Linux 5.8 server. Which I did.
The problem is that the Linux Admins can't detect the added space. They use native Linux Multipathing (multipath -d, multipath -ll). Not EMC PowerPath. They still see a 10 GB volume, even though I changed it to 20 GB.
We do this all of the tiem with the W2K8 Admins, but we have never done this before with the Linux servers.
I told them that the Linux OS is "remembering" the old volume attibutes, and that they need to get it to "see" the new space. They have been messing around (rescan, 'echo "- - -" blah, blah, .....'), but they can't get it to work on the fly. The best they come up with is I remove the LUN from the server, they reboot the server, which wipes out the old LUN characteristics, and then I replace the LUN with the same "local LUN number", and then they see the new space. Also, if I change the "local LUN number" then Linux sees it as a new volume and sees the new space.
Is there some kind of Linux command to "recognize" the new attribute of the LUN:
echo "- - -" blah, blah, recognize-new...
If W2K8 can do it, then RHEL should be able to do it!
In point of fact they are using OCFS2, which is an Oracle File System. However, the problem is before they get to Oracle. RHEL sees 10 Gb instead of 20 GB.
A modern OS should be able to expand a PV on the fly. Windows can do it. New HP-UX (11.31) can do it (I'm told). Linux should be able to do it.
More info: "inq" sees the 20 GB full size. It's "multipath -ll" that only sees the original 10 GB. The problem is we have to get "multipath" to recognize new device size.
Have you tried restarting multipathd to get it to see the new size
Run "blockdev --rereadpt /dev/<sd??>" on the device to make sure that the OS recognizes its new size.
Check again, to see if the multipath -ll reflects the size if not you can try restarting multipath
1. service multipathd stop
2. service multipathd start