On Thu, Apr 03, 2008 at 07:34:58AM +0200, Jesper Krogh wrote:
> 
> Hi.
> 
> I have an Equalogic iSCSI array that has 3 x 1gbit interfaces. Do I have 
> to do anything to the software initiator to make it utillize the 
> redundancy? Or does it automatically shift the connection to one of the
> other ip-adresses if one of the links go down?
> 

Equallogic array does automatic loadbalancing (connection redirection) on
the array end.. also on the fly when load changes.

But you also need to have multiple connections through multiple NICs or HBAs
from the server to the array.. to handle the NIC/HBA/network/switch failures. 

If you're using software open-iscsi you should configure open-iscsi to bind
separate iscsi session to all of the NICs.. and then run dm-multipath on top of
these sessions to create a loadbalanced and redundant connection to the
array.

See open-iscsi documentation about binding iSCSI sessions to 
NIC/IP/MAC/interface.

/var/lib/iscsi/ifaces/

iface0:
        iface.iscsi_ifacename = iface0
        iface.net_ifacename = eth0
        <iface.hwaddress = 00:0F:1F:92:6B:BF>
        iface.transport_name = tcp

So you can create multiple interfaces (ifaceX), one for each NIC you have..


> Another (somewhat related) question. We borrowed the first array and 
> Equalogic has a feature where you can just add new arrays to the pool. 
> It will then have say 6 x 1gbit interfaces for a time.. then you can 
> tell it to move the data/volumes to the other array and you can power 
> off the old one. The Portal-Ip-adresse remains the same under the 
> operation but the ip-adresses that sucks up the data doesn't.
> 
> How is the software initiator supposed to handle this situation?
> 

iSCSI protocol supports "redirection" commands, and Equallogic uses these to
redirect the initiator to new/correct interface on the array..

> (for the record, it blew up with scsi-errors and turned my filesystems 
> read-only)
> 

What did you actually do when this happened? 

Which distribution are you running? Which kernel? Which open-iscsi version?
open-iscsi from the distribution or from open-iscsi.org ? 

-- Pasi

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