On Thu, Jul 02, 2009 at 09:41:30AM -0400, Hoot, Joseph wrote:
> 
> Hi all,
> 
> I'm currently attempting to implement a Dell EqualLogic iSCSI solution
> connected through m1000e switches to Dell m610 blades with (2) iSCSI
> dedicated nics in each blade running Oracle VM Server v2.1.5 (which, I
> believe, is based off of RHEL5.1).
> 
> [r...@oim6102501 log]# rpm -qa | grep iscsi
> iscsi-initiator-utils-6.2.0.868-0.7.el5
> [r...@oim6102501 log]# uname -a
> Linux oim6102501 2.6.18-8.1.15.3.1.el5xen #1 SMP Tue May 12 19:21:30 EDT
> 2009 i686 i686 i386 GNU/Linux
> 
> I have setup a bond with the two nics to test this out initially and had
> no problems.  This allows for failover (active-passive bond).  I
> discovered my targets, I logged into sessions, and recognized everything
> from dm-multipath.  I fdisked, formatted drives, and mounted them.    I
> then ran lots of dd's to and from the disks with speeds around 90MB/sec
> when `dd if=/dev/mapper/ovm-1-lun0p1 of=/dev/null bs=1M count=1000`
> 
> So since this is going to be one of many VM servers in our OVM cluster
> with multiple VM's running on it (of which many are database servers), I
> wanted to try to make this more efficient.  Therefore, I read that by
> using the `iscsiadm -m iface` syntax you can (instead of bonding) setup
> (2) nics individually, each with an IP on that same segment as your
> iSCSI storage.  From what I understand, this allows (2) sessions to be
> created to each volume-- which should give you a little more throughput.
> I did this:
> 
> iscsiadm -m iface -I eth2 --op=new
> iscsiadm -m iface -I eth3 --op=new
> iscsiadm -m iface -I eth2 --op=update -n iface.hwaddress -v
> 00:10:18:3A:5B:6C
> iscsiadm -m iface -I eth3 --op=update -n iface.hwaddress -v
> 00:10:18:3A:5B:6E
> iscsiadm -m discovery -t st -p 192.168.0.19 -P 1
> iscsiadm -m node --loginall=all
> 
> dm-multipath sees 2 paths now to each volume.  If I run `iscsiadm -m
> session -P 3` I can see which /dev/sdX device is used by which multipath
> device.  I have multipath setup to load balance across both paths with
> rr_min_io set to 10 in /etc/multipath.conf (which it is my understanding
> that this will send 10 I/Os to one path and then switch to the other
> path).
> 
> my eth2 is 192.168.0.151
> my eth3 is 192.168.0.161
> 
> my group is 192.168.0.19
> my eql interface#1 is 192.168.0.30
> my eql interface#1 is 192.168.0.31
> 
> [r...@oim6102501 log]# netstat -rn
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags   MSS Window  irtt
> Iface
> 10.0.10.0       0.0.0.0         255.255.255.0   U         0 0          0
> vlan10
> 169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0
> eth3
> 192.168.0.0     0.0.0.0         255.255.0.0     U         0 0          0
> eth2
> 192.168.0.0     0.0.0.0         255.255.0.0     U         0 0          0
> eth3
> 0.0.0.0         10.0.10.254     0.0.0.0         UG        0 0          0
> vlan10
> 
> PROBLEM:
> ========
> I'm now having some odd issues where everything appears to work fine.  I
> can mount drives and dd stuff around.  But then I will occasionally get
> "Reset received on the connection" from my EqualLogic logs.  I will see
> the same thing in /var/log/messages from my kernel scsi layer as well as
> dm-multipath layer.  When I look at `iscsiadm -m session -P 2` I can see
> the following: 
> 
> iSCSI Connection State: TRANSPORT WAIT
> iSCSI Session State: Unknown
> Internal iscsid Session State: REPOEN
> 
> By the way, is that a bug?  "REPOEN"?  should it be "REOPEN"?
> 
> Within about 1-2 minutes it will reconnect.  But I'm a bit baffled what
> would cause this.
> 
> QUESTION:
> =========
> Since I am creating two iscsi sessions (one out eth2 and eth3), I'm
> wondering how routing plays into sessions.  Since iscsiadm is given the
> hwaddress, does iscsid need to care much about routing?  In other words,
> let's say that, for whatever reason, my session that I had through eth3
> (that session, by the way, is connected to 192.168.0.31 on the
> EqualLogic) timesout.  iscsid sees this and attempts to REOPEN the
> session.  Since my routing table shows eth2 above the route for eth3,
> IP-wise, eth2 will be the interface that would typically be chosen for
> that traffic to route out of.  However, is iscsid smart enough to not
> use that route and instead select the iface (based on hwaddress) to use
> for that reconnection?
> 

You can also use the ethernet interface name, to make sure correct iface is 
always used.

# iscsiadm -m iface -I iface3 -o new
New interface iface3 added

# iscsiadm -m iface -I iface3 --op=update -n iface.net_ifacename -v eth1.234
iface3 updated.

Replace the eth1.234 VLAN with whatever you use, for example eth3.

You can also specify these things in /var/lib/iscsi/ifaces/ directory.
Create a file called "ifaceX" and write something like this in it:

iface.iscsi_ifacename = ifaceX
iface.transport_name = tcp
iface.net_ifacename = eth0.xyz

or you could replace the iface.net_ifacename with

iface.hwaddress = 00:DE:AD:BE:EF:00

if needed.

-- Pasi

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