Questions on EMC powerpath

[Kishore Gowda]

Hello,

We have a production server (RP8400) connected to Symmetrix 8430 via dual fiber path. I am using PVLINK for alternate pathing / manual load balancing. However, we recently purchased a license for powerpath and planning to install the software this weekend. Given this is a production server, I am a little nervous about installing powerpath. Some of the questions I am pondering on PP install:

1. Do I need to remove PVLINK prior to PowerPath install?
2. Does PP configuration make any LVM changes? (specifically device path changes)
3. Does PP requires any HP-UX kernel changes?
4. Any other risks on installing PP over PV.

Thanks for your time.

Kishore

[Marco Santerre]

Though it is someone else that has gone through the upgrade in our team, I can tell you this.

You don't need to remove/add any PVlinks from your VG configuration in order to install PowerPath. Nor do you need to make any LVM config changes.

PowerPath seems to work from the LVM part. Basically, in layman's term, how I understand it. As soon as a request is sent to a disk on LVM, Powerpath recognizes that and redistributes the load to balance all FC.

I know that PowerPath installs via swinstall and requires a reboot. I don't know if the reboot is due to a kernel change.

We didn't have any issues installing it nor do we have any running it.

[Chris Vail]

Its been a few months since I messed with it, but PowerPath makes PVlinks redundant. You can leave them in if you'd like, but there's no reason for this.
No LVM changes made: no device path changes, plus no kernel changes. Installation is easy, requiring a reboot only.
This is a GREAT piece of software--no downsides technically that I can think of. Its a little pricey, but does'nt have an appreciable effect on CPU utilization. If the boss'll buy it, its a worthwhile item.

Chris

[Todd McDaniel_1 · Accepted solution]

Powerpath is an awesome tool!

Powerpath superceedes PVlinks, but I keep the alt links just for my own accounting of my alternate paths.

Technically you can remove the pvlinks ALT pathing and Powerpath would find it via the hypervolume number and route your data thru the alternate h/w path if you ever had a HBA failure.

There are no kernel requirements for PP that I can remember. I loaded it on 2 other boxes of mine as well. My Primary DEV and TEST boxes...

PP is not merely great for Load balancing on Production or high use DEV boxes. It can help you manage systems with large quantities of attached storage. The tools you gain are invaluable.... inq/syminq for 2...

Also you gain a whole suite of "powermt" tools that enable you to manage your disks on the frame. AFAIK, PP is compatible with all major Frame types.

After you load it look for these procs...

# ps -aef|grep emc
root 100 1 0 Jan 17 ? 0:10 /etc/emcpdaemon
root 101 0 0 Jan 17 ? 1:31 emcpd
root 102 0 0 Jan 17 ? 0:00 emcpdfd
root 103 0 0 Jan 17 ? 0:10 emcpwdd
root 104 0 0 Jan 17 ? 0:01 emcpstratd

In addition we also use "EMCControl Center 5.1" on our boxes... Instead of having to shutdown your frames everytime for mainenance upgrades, ECC5.1 allows for management of your bin files via online changes thru workstations... After the initial binfiles are created, you can manage your entire array online!

[Jordan Bean]

Hello Kishore,

1. No. PVlinks are irrelevant to PowerPath.
2. No. PowerPath has nothing to do with LVM.
3. Yes. A new kernel module is installed, but no changes are made to the usual kernel parameters.
4. Make sure HP-UX is current on all patches. If you're installing it on a K-class running HP-UX 11.00, then you may need to enable the spt0 (scsi pass-thru) driver.

This is a typical installation:
Install PowerPath base and reboot.
Install PowerPath patch and reboot.
emcpreg -install (enter license key)
powermt config
powermt save
powermt display
Done.

As of this post, the latest available version for HP-UX is PowerPath 4.1.0.

I haven't seen the latest documentation, but it may recommend bringing the host up on one scsi/fiber channel while installing PowerPath, then enabling the other channels and running powermt config in succession. As far as I know, this hasn't been necessary since version 2.

[Mic V.]

Hi, Kishore,

I did an upgrade about two months ago. Like you, I was very nervous -- I didn't want EMC software in the middle of my HP (chocolate in my peanut butter?? :). But it actually went fine.

1. No.
2. Not on HP-UX, but it does make interesting changes on other platforms. I think I remember being told that on AIX, you end up with no native disk names and only PowerPath names; on Solaris, you could refer to either the native or PowerPath names.
3. Yes, as I recall it loads a new driver.
4. Not that I'm aware of.

I interrogated both EMC and HP; both assured me it would be fine. I even talked to a back-line CSS guy, who said he really hadn't seen any issues.

YMMV, but I'd say go ahead and jump. :)

Mic

[Todd McDaniel_1]

no points here...


Just as a followup... I have had ZERO issues with PowerPath. One box I have had it loaded for over 4 years, almost 5 years, with NO issues.

I currently have it loaded on 3 hosts... I have over 6-7TB of disks controlled by PP. on 4 frames. And I will be adding another 12TB (5TB Actual used and the rest for H/w mirroring and BCVs)

Of course, there is the occasional Software patch or firmware upgrade on the frame.

Great product and very minimal cpu utilization...