Help with ISCSI SAN

Clint Dilks clintd at scms.waikato.ac.nz
Mon Feb 1 13:59:54 CST 2010


Hi Paul,

Thanks for the response.  I actually now have physical access to the kit 
we have bought and it turns out I mis-understood exactly what we have.  
Rather than purchasing HBA's we have purchased network cards that do 
ISCSI offloading I believe its called iSOE.

I have been able to set up one system using software ISCSI initiation 
and ignoring iSOE so now the plan for this week is to see if I can get 
iSOE working and compare the two systems :)


Paul M. Dyer wrote:
> Hi Clint,
>
> My feeling is that the NIC on the server is not where most multipath happens.   You could use bonding for 2 NICs to have a secondary NIC take over if the path from server NIC-1 gets disconnected.
>
> On the other end is where multipath takes place.   On a setup that I have, multipath logs in to 4 different paths on the SAN, and shows the paths with "multipath -l":
>
> xr (36006016025302300a2f50e7c0981de11) dm-10 DGC,RAID 1
> [size=24G][features=1 queue_if_no_path][hwhandler=1 emc][rw]
> \_ round-robin 0 [prio=0][active]
>  \_ 1:0:0:6 sdz  65:144 [active][undef]
>  \_ 3:0:0:6 sdaa 65:160 [active][undef]
> \_ round-robin 0 [prio=0][enabled]
>  \_ 2:0:0:6 sdab 65:176 [active][undef]
>  \_ 4:0:0:6 sdac 65:192 [active][undef]
>
>
> Paul
>
>
>
> ----- Original Message -----
> From: "Clint Dilks" <clintd at scms.waikato.ac.nz>
> To: linux-poweredge at dell.com
> Sent: Tuesday, January 12, 2010 9:09:09 PM (GMT-0600) America/Chicago
> Subject: Help with ISCSI  SAN 
>
> Hello Everyone
>
> I am wanting feed back from people familiar with Dell Equallogic ISCSI SANS.
>
> Our organization has just purchased a  Dell Equallogic ISCSI SAN with 
> all the equipment required to allow a host to have fully redundant paths 
> to this SAN.
>
> We have also purchased PowerEdge Servers with Broadcom NetXtremeII Nics 
> /ISCSI HBA's.  On some of these servers we want to run Redhat Enterprise 
> Linux 5.4 or CentOS 5.4
>
> I can find documentation on using Software ISCSI initiators, but nothing 
> on using Broadcom Hardware HBA's so I am assuming it is a case of go 
> into the BIOS of the server put in the license key for the Hardware HBA 
> and then another device that looks like a Nic will be present  once RHEL 
> or CentOS is installed.  Is this correct ?
>
> If this is the case I am assuming I still use the open iscsi initiator 
> tools to manage things ?
>
> To ensure redundancy each Linux host will have two nics going connected 
> to the ISCSI network. And I am aware that I can use dmsetup / multipath 
> to setup a redundant device but one thing that confuses me is that if 
> the two nics (each connected to a separate switch) are on the same 
> subnet (as Dell have instructed me to  do)  how can you guarantee that 
> the two connections you see are using the appropriate redundant paths ?  
> Or is this not really an issue ?
>
>
> Thank you for any thoughts or experiences that you can share related to 
> a setup like this, and have a nice day :)
>
>
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