HPUX 11.00: Installation of EMC Power Path Into Existing MCSG Cluster

[LG Porter]

I have a MC/ServiceGuard Cluster composed of three N4000 servers running HPUX 11.0 and MCSG 11.09 connected to a EMC Symmetrix 8730 array. Within the next several weeks, I'm planning on installing EMC Power Path product. The cluster now has pvlinks setup. a) Can I leave the pvlinks in place after installing PowerPath or do they need to be removed? Is there any good ITRC docs that refernnce Power Path and pvlinks? B) Just prior to installing the PowerPath, should the SG packages be moved over to the failover nodes? C) After installaion of PowerPath, and setup of the powerpath_registeration number, is there any additional iteams that should be performed at the server level. D) What is a good check to verify that Power Path is installed and working correctly?

[melvyn burnard · Accepted solution]

Well I do know we support the use of PP inan Sg cluster, but do not actually know hte product, so I will try to answer what I can:

a) Can I leave the pvlinks in place after installing PowerPath or do they need to be removed?
EMC recommends that HA users still configure PVLinks and alternate paths when PowerPath is used. While this is not absolutely necessary, it is useful for understanding what the physical hardware configuration actually looks like.

B) Just prior to installing the PowerPath, should the SG packages be moved over to the failover nodes?
I believe thatt installing PowerPath may affect the kernel,(but could be wrong) and hence cause a kernel b uld and reboot. If this is so, then yes, move all the packages, and do a cmhaltnode first

C) After installaion of PowerPath, and setup of the powerpath_registeration number, is there any additional iteams that should be performed at the server level?
and
D) What is a good check to verify that Power Path is installed and working correctly?

I do not know, I suggest reading the PowerPath documentation

Just some additional notes:
When running cmquerycl, it is possible for a PVLink that is down to be listed as up, since PowerPath will make it appear to be up as long as one of the alternate paths to a device is still up. When a path to a device goes down, PowerPath will log that to the syslog.log file, so it is not a silent problem.
When any PVLink goes down, ServiceGuard may not know, as long as there is at least one link to the device still functioning. PowerPath will log any failed or returned PVLinks to the syslog.log file, but the user might not be aware that there is a problem unless they regularly scan the syslog.log file, or EMS is setup to notify them of a problem with PVLinks.

[Sunil Sharma_1]

Hi,

1. You can leave PV link intact.
2. Before installing Power Path you have to switch the pakage becoz power path required rebbots, it's rebuild kernel during Installation.
3. You have to run some command like
powercf -i
powermt config

for checking the functonlity i am doing this

copying some files from one disk to another and seeing the load on both link(path) using sar -d

Sunil

[Mark Greene_1]

D) What is a good check to verify that Power Path is installed and working correctly?

Once you have PP installed and it correctly reports the LUNs on the SAN via "powermt display", pull one of the cables from one of the HBAs. You should see PP move access to all of the disks to the remaining HBA.

HTH
mark

[Vasikaran Venkatesan]

a) U can - but not needed.
b) Better - I do not think installing PP needs reboot - as it builds the wrapper around devices and interfaces with the device calls - and i believe, it may not need a reboot also.
c) Not much - powerpath is very straight fwd.
d) powermt watch every= should show all the paths and if you have some io, u can see that all distributed on all paths. If you have 4 paths and 400 Mb of data transfer from one disk, u will see 100 Mb in each path.

[LG Porter]

Mark, please define what the meaning of the accronym "HBAs"? Thanks

[melvyn burnard]

HBA:
Host Bus Adapter
Fancy name for interface cards :-]

[Mark Greene_1]

Sorry. Yes, Host Bus Adaptor. It's how the EMC guys refer to the fibre controller cards.

If you haven't already, go to EMC's customer support site and sign-up:

http://powerlink.emc.com/

They have a lot of white papers and other documentation there.

mark