[Users] iSCSI multipath with EqualLogic SAN

Fri Feb 22 05:30:11 UTC 2013

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: Donnerstag, 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<mailto: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> [mailto: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<mailto: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> [mailto: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<mailto: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
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