Question

Can I disable EMC PowerPath and simply use /dev/sdb to mount an exiting volume in RHEL3

Asked by: aaran_stent2

I am trying to exit my Dell EMC SAN and virtualises the last remaining "physical" system we have.  Our server iba-prod uses a 200GB LUN on a CX300 SAN.

[root@iba-prod root]# df -k
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda5             54473944  43318756   8387996  84% /
/dev/sda3               101107     15721     80165  17% /boot
none                   2047704         0   2047704   0% /dev/shm
/dev/emcpowera1      206422036  54727956 141208460  28% /opt/iba
[root@iba-prod root]#

As you can see it is using EMC PowerPath, this is preventing the VMware converter from P2Ving the entire system.  This Issue has been documented here

http://communities.vmware.com/thread/199098

I can see 4 x drives available when i do an fdisk -l (1 for each path)

I would like to remove PowerPath and connect the /opt/iba volume using a native linux "dev" mapper.  Multipathing is not required.

Can I simply remove powerpath and then change the mount path in fstab to /dev/sdb for /opt/iba without losing data?

I found an experts exchange question similar to my issue but on Solaris.  They had issues with the Sun LVM not being able to recognise the LUN after power path was removed.

http://www.experts-exchange.com/Storage/Storage_Technology/Q_23614489.html

I only need this to work for 2 hours while I P2V the machine in VMware converter.

Aaran

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Asked On
2009-10-14 at 16:38:45ID24813328
Tags

EMC

,

Red Hat

Topics

Storage Technology

,

Red Hat Linux

,

VMware

Participating Experts
2
Points
500
Comments
7

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Answers

 

by: meyersdPosted on 2009-10-14 at 20:43:47ID: 25577044

Yes, you can. PowerPath provides persistemt binding as well as multi-pathing. You may find that the device changes from /dev/sdb, but it will still be there and you'll still be able to access the data without any worries.

I've struck a few issues with virtualising IBA PAS systems in 4000+ seat environments - the virtualised system wouldn't behave - it wanted 16 cores to call its own. This was under ESX 3.5, so if you're on vSphere, you may have a happier experience, but I'd have a back-out plan ready if I were you.

 

by: aaran_stent2Posted on 2009-10-14 at 21:09:54ID: 25577148

Thanks for the reply.  I was trying to test this with my test blade.  With a single user on performance "appeared" to be good.  My test system is not in a particularly useful state for functional or performance tests so I am going to clone production and test it tomorrow.

I don't have 4000  staff let alone 4000 seats.  We have less than 1000 beds.  Thanks for the specific feedback on the application I will consider myself warned.  I have heard of success stories on implementations up to my size and even above it.

I will uninstall the driver tonight and let you know how I get on.  (and award the points)

Still hoping to migrate for real on Sunday morning.

 

by: meyersdPosted on 2009-10-14 at 23:37:04ID: 25577800

No worries! You should be right. One hospital I worked with had IBA PAS running on a quad processor, dual core Dell box with 16GB RAM and it didn't appreciate the migration into VMware, so after a load of testing it was spun back out to physical. I suspect that it would probably run fine under vSphere, but (not surpisingly) the hospital is reluctant to try again. The performance issues pretty much came down to latency on disk I/O - something that has been improved massively in the latest release of VMware.

 

by: thribhuPosted on 2009-10-15 at 12:12:53ID: 25583728

Hi,
There should be no I/O on the paths during the change over to avoid the data loss.
Is it a powerpath or powervolume.
Before you uninstall the powerpath, try mounting this lun on diff test box if any.(See to that no I/O on this lun for any changes)

What ever is the case you will not loose any data , might need filesystem downtime hardly.

 

by: aaran_stent2Posted on 2009-10-15 at 13:53:22ID: 25584797

Ok it worked.  I wanted to find a way to disable rather than uninstall the driver.  I wanted the simplest may to get back up and running as possible.  I scheduled a user outage.   run "shutdown" for some warning and went to run level 1.  Moved the /etc/init.d/PowerPath startup script to another directory, commented out the /dev/powerpatha line in /etc/fstab  and restarted.

Upon running an fdisk -l i swa the volume was available more than once, is chose the first valid looking partition /dev/sdc1 and modified the /etc/fstab.  Did another reboot to ensure that the services all started cleanly with the mount in place and all was good.

I was then able to run the VMware P2V and convert the machine to VMware.

Thanks experts-exchange for your help

 

by: aaran_stent2Posted on 2009-10-15 at 13:55:33ID: 31641394

In hindsight I should have asked for the specific steps on how to "Disable" the adaptor.

 

by: meyersdPosted on 2009-10-15 at 14:33:43ID: 25585146

Thanks! Glad I could help.

20120131-EE-VQP-002

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