topic Re: Multipath with kernel MPIO or Qlogic drivers? in Operating System - Linux

Multipath with kernel MPIO or Qlogic drivers?

Andrew Hunter_2 — Thu, 10 Nov 2005 01:58:45 GMT

We have ordered a DL585 with 2 x FCA2214 and running Suse Linux Enterprise Server 9 (SLES 9). This will be connected to an EMC CX500 through an EMC DC24(?) FC switch. 2 FC paths to the switch and 2 FC paths from the switch to the storage array.

The SLES 9 doco (for SP2) mentions the availability of MPIO in the kernel (module?).

I know the Qlogic drivers support multipath failover themselves.

Where is the best place (tool) to implement multipath failover?

Re: Multipath with kernel MPIO or Qlogic drivers?

Luk Vandenbussche — Thu, 10 Nov 2005 02:32:13 GMT

Hi,

In our environment we always use the Qlogic driver. We don't have any bad experience with this driver

Re: Multipath with kernel MPIO or Qlogic drivers?

Kodjo Agbenu — Thu, 10 Nov 2005 16:59:16 GMT

Hello,

The main advantage of implementing multipath at the lowest level (Qlogic driver) is more flexibility offered in operating system configuration. For example : device naming convention stay standard (/dev/sdXXX or /dev/cciss/...).

My feeling is that it would be better for performance too, but I have no facts to argue that.

Good lcuk.
Kodjo

Re: Multipath with kernel MPIO or Qlogic drivers?

Serviceguard for Linux — Thu, 10 Nov 2005 23:26:51 GMT

If you are using an EMC array, you should check with EMC on the appropriate multipath. They do not support the same multipath mechanisms that HP does. You should still use the HP version of the QLogic driver. I believe that EMC will support that, but still check to ensure that the two parts of you're configuration are supported by both HP and EMC.

Re: Multipath with kernel MPIO or Qlogic drivers?

Andrew Hunter_2 — Fri, 11 Nov 2005 00:31:05 GMT

This is where it get's interesting.

Given the config mentioned at the start of this thread (inlc. SLES9 SP2);
EMC's doco states - "Neither PowerPath nor the v2.6.x kernel native failover (MPIO) functionality is supported with this Linux distribution."

Suse explicitly mention EMC Clarion CX as supported by the kernel MPIO in SLES9 SP2. In fact it is the "only" MPIO that Novell support in SLES9.

I haven't found much from Qlogic yet.

HP has doco on Qlogic multipath but with no mention of Clarion's.
http://h20000.www2.hp.com/bizsupport/TechSupport/CoreRedirect.jsp?redirectReason=DocIndexPDF&prodSeriesId=421487&targetPage=http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00169487/c00169487.pdf

Which of these takes precedent or more importantly who do I trust our company infrastructure to?

I realise that having single server and storage vendor would have simplified things but that hasn't happened.

Re: Multipath with kernel MPIO or Qlogic drivers?

Kodjo Agbenu — Fri, 11 Nov 2005 02:19:17 GMT

Hi,

Who is going to support the solution ? If you purchased the SuSE distro from HP, then it is HP. In that case I would recommend that you follow HP recommendations.

Good lcuk.
Kodjo

Re: Multipath with kernel MPIO or Qlogic drivers?

Andrew Hunter_2 — Wed, 30 Nov 2005 03:20:21 GMT

Update and summary

Qlogic - recommended by a couple of posts here.
Kernel MPIO - supported by Suse.

Vendor positions
EMC: Qlogic is a no go (word of mouth). Linux kernel MPIO is unlikely to be supported for reasons of "investment" (email, awaiting official letter).
HP: do whatever EMC tell you to do.

Further advice always appreciated.