RE: HP EVA + Qlogic HBA + failover

[Stephen Gardner <stephen-rhel uk org>]

On Thu, 21 Apr 2005, Mimmus wrote:

> In my experience, RH qla2300 driver supports failover in RH 3 >= U4, before
> not.
> I tried to pull one of the cables to my switches (I use an HP EVA 3000
> disk-array) and system still works (logging failover to syslog).
>
> Notice that in 2.6 kernels FC support was completely rewritten (no failover
> in driver, peraphs you need to use md) and it is currently in evolution:
> http://kerneltrap.org/node/5022

There's just been a discussion similar to this on the nahant-list 
regarding multipathing so I'll add a couple of notes if you do plan a 
RHEL3 -> RHEL4 upgrade in the future. As Domenico says this changed in the 
v2.6 kernel and therefore in RHEL4. The RHEL4 QLogic drivers don't have 
failover built-in (unlike RHEL3) and the end-game is to have multipathing 
abstracted into the device-mapper layer, superceding md multipating. But 
it'll be RHEL4-U2 before device-mapper multipathing is a reality. Although 
simplistic I think I can say that

- qla driver multipathing / failover isn't in RHEL4
- md multipathing will be superceded but is still present in RHEL4
- device-mapper (dm) multipathing won't be with us until later in the
  RHEL4 life-cycle (probably U2), although the kernel modules will go in
  in RHEL4-U1

Having read the kerneltrap piece it seems this whole area is in flux at 
the moment.

Regards,
   Stephen

> > From: taroon-list-bounces redhat com
> > [mailto:taroon-list-bounces redhat com] On Behalf Of Gabor MICSKO
> > Sent: Thursday, April 21, 2005 5:11 PM
> > To: taroon-list redhat com
> > Subject: HP EVA + Qlogic HBA + failover
> >
> > Machine: HP Proliant DL380
> > Storage: HP Enterprise Virtual Array 3000
> > OS: Red Hat Enterprise Linux AS release 3 (Taroon Update)
> > Kernel: 2.4.21-15.ELsmp
> >
> > I have two QLogic Corp. QLA2312 Fibre Channel Adapter in HP
> > Proliant. I want to have redundant link to EVA (if one HBA
> > fails -> failover to second HBA).
> >
> > My questions:
> >
> > 1.) Is the qla2300 driver in Taroon failover ready?
> > 2.) If I load the qla2300 with parameter 'ql2xfailover=1'
> > (insmod qla2300 ql2xfailover=1), is this enough for a full
> > failover-configuration or do I need to set something else?
> >
> > Thanks
> >
> > --
> > Micskó Gábor
> > HP Accredited Platform Specialist, System Engineer (APS, ASE)
> > Szintézis Computer Rendszerház Rt.
> > H-9021 Győr, Tihanyi Árpád út 2.
> > Tel: +36-96-502-216
> > Fax: +36-96-318-658
> > E-mail: gmicsko szintezis hu
> > GPG Key fingerprint: 6FA1 D8BF 3C73 0570 ED5D  82AC A3BE 4E6A
> > CF95 5F50