topic Re: PV Links vs Secure Path in Operating System - HP-UX

PV Links vs Secure Path

Leslie Fischer — Tue, 30 May 2006 14:34:09 GMT

We are currently using HP-UX 11iV1 w/MCSG, in a 2 node Cluster with Veritas Replication to a DRP site. We also have an EVA 3000 and we have both LVM and VxVM drives configured on the SAN. We are currently using VxVm 3.5 on HP-UX 11.11 and connected to a SAN via two HBA cards & Secure Path.

We are scheduled to upgrade the hardware and we have been lookin at the Integrity Servers to replace the current PA Servers. Can VP Links replace Secure Path? Do you know if PV Links work with VxVm 4.1 or VxVm 3.5? I looked for a compatibility matrix but it did not list these products. I have heard that on HP-UX 11.23 w/ 2 HBA cards connecting to a EVA 4000, you could use PV links to replace using Secure Path. We plan on still running MCSG w/ 2 node cluster and Veritas Replication to a DRP site.

Does anyone know where I can find info on the PVlinks for HPUX 11.11 or HPUX 11.23?

Does anyone have a similar setup? Any pros or cons? Any information would be helpful.

Thanks
Leslie

Re: PV Links vs Secure Path

Torsten. — Tue, 30 May 2006 15:07:42 GMT

This may be interesting:

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00248530/c00248530.pdf?jumpid=reg_R1002_USEN

PV links is not a software, it is LVM functionality. You just tell LVM the different ways to one disk and LVM is switching to the next path if the first becomes unavailable. AFAIK Secure path is needed for Active/Passice arrays and can enhance LVM configurations with load sharing and some more, if the hardware can do this.
IMHO, secure path can replace or better enhance pv links, but not vice versa.

Re: PV Links vs Secure Path

melvyn burnard — Tue, 30 May 2006 15:10:34 GMT

for an EVA 3000 to support PVLinks, you need to install the very latest version of the VCS for the EVA.

Re: PV Links vs Secure Path

Olivier Masse — Tue, 30 May 2006 19:37:14 GMT

Currently PV Links is the poor man's solution, doing just link recovery and no load balancing. But you can't beat the price - it's free. Currently I use PV Links, as I couldn't justify buying SecurePath which is rather expensive.

But as someone mentioned be careful with 1st generation EVAs as PV Links won't work with active-passive arrays. Another thing, under PV Links you're on your own if you want to identify your devices and order them in LVM. You end up with 8 paths for each vdisk in ioscan so you have to be careful. SecurePath makes this easier by grouping the disks and identifying them by their wwn.

I think that there is a better path failover solution that is planned for a future release of HP-UX. This will make SecurePath redundant.

Olivier

Re: PV Links vs Secure Path

Chauhan Amit — Wed, 31 May 2006 01:37:13 GMT

Secure Path eliminates the RAID controller, Host Bus Adapter (HBA), and
interconnect hardware (cables, switches, and connectivity devices) as single
points of failure in the storage system.
By using redundant hardware and advanced RAID technology, Secure Path
enhances fault tolerance and storage system availability by providing automated
failover capability.
Redundant physical connections define separate paths in a Secure Path hardware
configuration. Each path originates at a unique HBA port on a server and ends at a
unique RAID controller port in the storage system.

The Secure Path software detects the failure of I/O operations on a failed path and
automatically re-routes traffic to other available paths. Secure Path software
gathers alternate paths through available SAN switches, controllers, controller
ports, and HBAs. Path failover is completed seamlessly, without process
disruption or data loss.

PVLinks is part of LVM functionality as explained above.

-Amit

Re: PV Links vs Secure Path

Albert_31 — Wed, 31 May 2006 02:13:48 GMT

Hello Leslie,

Regarding your queries..

a) PV links work with LVM only..it comes by default..you add alternate paths using the vgextend command.. LVM determines that it is pointing to the same disk/lun and adds it as an alternate path (called PV links)...it does not interact with VxVM..

b) EVA 3k has 2 host ports on each controller and depending on the SAN connection... you would see multiple paths for the same LUN. Secure Path is used to mask these multiple paths and provide only 1 path to the OS thereby easing administration. Since there is no Array support library for the EVa3k/5k...VxVM has no way to determine that they are multiple paths to the same LUN, thinks that each path is a separate device and acts accordingly .. which makes things difficult for the sysadmin..

c)EVA4k is the next generation of EVA storages and does not require secure path to mask the mulitple paths for the luns...the controller takes care of it now, hence you dont require to purchase securepath for eva4k,6k,8k..

regards

albert

Re: PV Links vs Secure Path

Zinky — Wed, 31 May 2006 09:37:18 GMT

Leslie,

Peace.

My advice to you is to simply drop LVM from the picture and use VxVM entirely -- even for your boot disks. This way you can drop SecurePath from the picture as your older EVA3000 can be upgraded to a new Firmware so it no longer requires SecurePath.
What will you be using then as path protection (which PVLinks and SecurePath do)? -- DMP. VxVM's DMP (dynamic multi-pathing) will now be your path protection and load balancing. It will fit nicely with the other Veritas solutions you now have and MCSG works perfectly with it. Also - did you know that you will no longer have to be worried about HW path (cXtYdZ) changes with VxVM?

Re: PV Links vs Secure Path

Leslie Fischer — Fri, 18 Jan 2008 18:55:49 GMT

Replaced with a EVA6000.

Re: PV Links vs Secure Path

Zinky — Sat, 19 Jan 2008 00:14:32 GMT

Leslie..
Peace.

So with this EVA6000 -- did you also went traight to Integrity Itanic Servers and HP-UX 11.31?

Are you still using VxVM? and still doing replication?

In your orginal post - you mentioned "Veritas Replication to a DRP site. "

Can you please expound on this if you don't mind? Are you using VVR (Veritas Volume Replication"? What's the size of your database(s?) and what's the bandwidth of your dark fibre or network between your main site and your DRP site?

Re: PV Links vs Secure Path

Leslie Fischer — Tue, 22 Jan 2008 22:23:56 GMT

We are using HP-UX 11.11 on PA8900's. We wanted to upgrade to Integrity, but the supporting OS was not approved by the Application vendor. So we are still using MCSG with VxVm 3.5 with VVR. Installed ASL to use the DMP with VxVm. We have two databases that are replicating to the DR site. Because of bandwidth issues on a T3, we can replicate only one database during production hours. The other one is paused 8am until 5pm and then resumed. It takes about 10 min to sync up the paused DB. The database sizes are 88gig and 140gig. Our SRL is 30gig for each DB. The SRL for the paused DB, fills up to about 5% for time it is paused. Both DB are on MCSG packages.

Re: PV Links vs Secure Path

Zinky — Tue, 22 Jan 2008 22:35:13 GMT

Leslie,

Muchas Gracias for the Info.

We're exactly the same boat. Stuck with PA8800/8900 CPUs and 11.11 and using EVA XL as well as XP.

We'll probably be able to get better than T3 (i.e OC3) bandwidth and I am in preliminary studies whether software based (VVR) will have advantages over array based replication (Continous Access or Hitachi Hi-Copy?).

What made you to stick with VVR instead of Continous Access perhaps? Do you find VVR pretty robust?

I'll really appreciate whatever info you can share man..

Re: PV Links vs Secure Path

Zinky — Tue, 22 Jan 2008 22:38:42 GMT

Forgot to ask.. are your DB Storage on cooked (Flesyetems) or raw storage? Do you also use VxVM for your boot disks?

BTW our databases are quite large... 400 GB to 3.2 TB. We're sil studying possible deltas (bits/blocks) -- any tool you've used in the past to assess?

Re: PV Links vs Secure Path

Zinky — Tue, 22 Jan 2008 22:38:59 GMT

Forgot to ask.. are your DB Storage on cooked (Filesystems) or raw storage? Do you also use VxVM for your boot disks?

BTW our databases are quite large... 400 GB to 3.2 TB. We're sil studying possible deltas (bits/blocks) -- any tool you've used in the past to assess?

Re: PV Links vs Secure Path

Leslie Fischer — Tue, 22 Jan 2008 23:07:49 GMT

We did not go with the CA solution a/o cost of the new investment of equipment required. We already had VVR in place and paid for the three year plan. We are goin to revist the CA solution at the next replacement or renewal. Hoping the cost of the equipment comes down. We are using cooked.

Re: PV Links vs Secure Path

Leslie Fischer — Wed, 23 Jan 2008 18:33:48 GMT

Used these tools to analyse the network traffic.

"http://www.apparentnetworks.com/sas/280/"

NetFlow Analyer 5

Leslie