[Users] iSCSI multipath with EqualLogic SAN

Fri Feb 22 10:22:38 UTC 2013

Hi all,

----- Mail original -----
> De: "Sven Knohsalla" <s.knohsalla at netbiscuits.com>
> À: "Chris Noffsinger" <cnoffsin at gmail.com>, "Jonathan Horne" <jhorne at skopos.us>
> Cc: "Baptiste AGASSE" <baptiste.agasse at lyra-network.com>, users at ovirt.org
> Envoyé: Vendredi 22 Février 2013 06:30:11
> Objet: AW: [Users] iSCSI multipath with EqualLogic SAN
> 
> 
> 
> 
> Never heard of HIT before.
> Seems to be a proprietary Dell solution?
> Ok, I just high-lighted the classical /most common SAN connection :)
> 
> We are using a Dell MD3220i (much smaller then EQ series) with MD1200
> units, and yes the network configuration for subnet separated
> multipathing seems to be more complicated at first,
> 
> but it will give you load-balancing and auto fail-over functionality.
> 
> Of course a nice and quick alternative as suggested here “…but you
> can configure your nodes to use the other paths using the command
> line on the Centos nodes…”,
> 
> is also possible.
> 
> 
> 
> Cheers,
> Sven.
> 
> 
> 
> Von: Chris Noffsinger [mailto:cnoffsin at gmail.com]
> Gesendet: Do nnerstag, 21. Februar 2013 20:05
> An: Jonathan Horne
> Cc: Sven Knohsalla; Baptiste AGASSE; users at ovirt.org
> Betreff: Re: [Users] iSCSI multipath with EqualLogic SAN
> 
> 
> 
> 
> We have 2 Equallogic PS4100s. And someone more knowledgeable may
> prove me wrong here but,
> 
> 
> 
> 
> Multipathd is not my most favorite thing to configure, but you can
> configure your nodes to use the other paths using the command line
> on the Centos nodes.
> 
> 
> 
> 
> 
> Yeah Dell will tell you that they want you to use their software
> (like the mem plugin in Vmware) but the Linux OS will see the other
> paths and treat it like any other SAN, you are just going to have to
> configure them to use them. The link sent earlier in the thread is
> the official guide to doing that.
> 
> 
> 
> 
> 
> https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/pdf/DM_Multipath/Red_Hat_Enterprise_Linux-6-DM_Multipath-en-US.pdf
> 
> 
> Here is another Doc I used that is for Rhel5 but I beleive the
> multipath commands are the same:
> 
> 
> 
> 
> 
> http://www.equallogic.com/WorkArea/downloadasset.aspx?id=8727
> 
> 
> 
> 
> 
> 
> 
> 
> On Thu, Feb 21, 2013 at 1:09 PM, Jonathan Horne < jhorne at skopos.us >
> wrote:
> 
> Ive discussed this at length with dell's EQ support team, and on a
> regular system that's connected in to an equallogic san, all the
> iscsi ports would be on the same subnet. The kicker is, dell really
> wants you to use their specialized driver/iscsiinitiator to access
> (known as their HIT kit...host integration tools), and the HIT kit
> handles establishing all the multiple sessions into the EQ SAN.
> 
> Unfortunately, equallogic doesnt support RHEV (and thus ovirt), and
> ovirt does not seem to execute the commands the HIT driver would
> want to intitiate multiple connections.
> 
> Dell says that the use of bonding for iscsi just begs for tcp
> retransmits. since bonding is the only method of failover I see for
> now, were using anyway against their recommendations (so far zero
> retransmits, but were not running our systems hard yet).
> 
> Cheers,
> Jonathan
> 
> -----Original Message-----
> From: users-bounces at ovirt.org [mailto: users-bounces at ovirt.org ] On
> Behalf Of Sven Knohsalla
> Sent: Thursday, February 21, 2013 8:55 AM
> To: Baptiste AGASSE
> Cc: users at ovirt.org
> Subject: Re: [Users] iSCSI multipath with EqualLogic SAN
> 
> Hi Baptiste,
> 
> usually a SAN doesn't support bonding (see post of Nicolas) of its
> interfaces, so you have to use multipathing technology.
> 
> You have to separate all nics in different subnets so multipath can
> work.
> Command multipath -ll with show the connected paths.
> 
> If you "merge" all paths in one subnet you will have the
> result/behavior you just posted.
> 
> So this is less oVirt related, more network specific.
> We have a running iSCSI config with 4 networks and oVirt runs well.
> 
> Maybe the following link will help you here:
> https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/pdf/DM_Multipath/Red_Hat_Enterprise_Linux-6-DM_Multipath-en-US.pdf
> 
> Cheers,
> Sven.
> 
> -----Ursprüngliche Nachricht-----
> Von: users-bounces at ovirt.org [mailto: users-bounces at ovirt.org ] Im
> Auftrag von Nicolas Ecarnot
> Gesendet: Donnerstag, 21. Februar 2013 15:48
> An: users at ovirt.org
> Betreff: Re: [Users] iSCSI multipath with EqualLogic SAN
> 
> Le 21/02/2013 11:30, Baptiste AGASSE a écrit :
> > Hi all,
> > 
> > I'm testing ovirt 3.1 on centos boxes. I setup ovirt management
> > node
> > and 4 vdsm hosts. vdsm hosts have 2 nics on the SAN subnet. When i
> > create a iscsi storage domain, it use only one of the two nics on
> > the
> > SAN network (showed with iscsiadm -m session on vdsm nodes). Does
> > ovirt support multiples nics on the same subnet for iscsi SAN
> > connection ?
> 
> I don't know if this is the best setup, but this is exaclty what I
> did (iSCSI with an Equllogic SAN) : I bonded 4 interfaces of the
> iSCSI subnet, and it's working fine so far...
> 
> --
> Nicolas Ecarnot
> 
> --
> Chris Noffsinger

More precision,

I use at this time in production el5/el6 clusters for years (xen|kvm + cman + rgmanager) with 2 nics on the same subnet (with 2 IPs addrs in this subnet, as equallogic want) + multipathd. It works fine and i'm happy with it.
I don't use equallogic HIT Kit because i've multiple type of SANs (tgtd and equallogic) connected to my hosts.

I want to test the same configuration with ovirt because it privides HA (as my el clusters), work with KVM and provides more features related to virtualization than my "basic" clusters.

When i've added storage domain in my ovirt 3.1 test env, it only setup one iscsi connection to the LUN on the vdsm hosts. Maybe there is a problem with my vdsm hosts configurations or ovirt-engine. I just wanted to know if someone with the same config (2 nics on the same subnet, equallogic SAN) have setup multipath to access storage domain. 

Nicolas said that he have similar config, so ovirt support it and it's a problem on my test env, i will investigate this later.

Thanks all for yours comments.

Have a nice day.

Regards.

Baptiste.