I haven't tested this, but you could give it a shot on a test box:

Stop PowerPath and iSCSI
/etc/init.d/PowerPath stop
/etc/init.d/iscsi stop

Restart iSCSI and PowerPath
/etc/init.d/iscsi start
/etc/init.d/PowerPath start

This should force PowerPath to rescan devices and pick up the new capacity, let us know if it works.

OK so it won't let you do this online, you would have to unmount any open devices, then stop iSCSI and PP, restart. Since you have to take the FS offline, you may as well reboot the box.

This is the first thing I tried. I get the following message:

Stopping PowerPath: PowerPath devices are open.
Please close these devices and then re-issue PowerPath stop.
failed

What I am trying to achieve is getting the psuedo device to see the LUN resize without rebooting the system. I can dynamically resize my partitions after that.

What I am looking for is a method to get the pseudo device to either rescan or recreate. It looks like it can be done with Windows but not with linux.

So there is no way on linux to get the pseudo device to rescan itself without taking down the system?

rescan for new devices ? If it's for new devices ...as soon as i present new LUNs i can see native device names show up in dmesg, then i can run powermt config and they get claimed by Powerpath and i can see my new power devices. I will be honest that it works 80% of the time on my RH 4U6 boxes, in other instances i have to reboot the box.

...growing a pseudo device I mean, not striking a balance between uptime and disk allocation.

What I was trying to accomplish was to get the emcpowera pseudo device to see a LUN resize. Native devices sdb, sdc and sdd (all the same device on different paths) see the new size after rescanning the iscsi target.

I have added another disk instead of growing the disk and have been able to see the new disk. I am runnning suse 10.2 and can run a rescan-scsi-bus.sh followed up by a scsidev -M -v which will allow the disk to be seen and a new pseudo device is created at that point.

I am trying to avoid allocating too much disk and am also trying to avoid having to take the system down. Has anyone been able to accomplish this?

This might work, For your expanded emcpower device run the following commands to remove it from PP config, and add it back again:

powermt remove dev=emcpowerX
powermt save
powermt config
powermt save

Now check if the device capacity has changed following the rediscovery.

if power device is mounted i don't see PowerPath letting you remove it from its config ?

True - thx Dynamox!

xbyx - have you seen Primus emc122304, its quite long but uses sfdisk -R on the emcpower device to re-read the partition information...

that sounds like more of managing the partitions on the disk rather an extending the disk online..

A sfdisk -R /dev/emcpowera gives me a BLKRRPART: Device or resource busy result.

Doesn't look like it can be done, but I've learned a lot along the way.

How do you submit an enhancement request to EMC? Maybe they could build the functionality into a future powerpath release.

Thanks to everyone who replied,

navigate to this area in PowerLink:

Home > Support > Request Support > Request a Product Enhancement