Design Questions
Arturo 'Buanzo' Busleiman
First of all: I've done my research in the eMail Archives before
deciding to disturb in here. Maybe I'm not googling for the perfect
keyword set. Anyway, here's my question:
I have:
* a PowerEdge 2950 with two nics with 4 ports total (e1000 and broadcom).
* a MD3000i PowerVault
* Vmware Server running on the poweredge.
I'm storing virtual machines in /vmstore (a
big partition on the poweredge's own RAID-5 virtual disk). The local
storage is for the OS and applications. Not the data.
So, the obvious question here: I want to store the data in the SAN.
Should I get my sessions running in the host, or inside each virtual
machine?
Also, is it OK to use multi path (dual path) using one broadcom port,
and one e1000 port (instead of using the two ports of the same nic)?
Any hints? Suggestions?
Thanks a LOT. I'm very new to this, but I'm doing my best effort.
Arturo 'Buanzo' Busleiman
> So, the obvious question here: I want to store the data in the SAN.
> Should I get my sessions running in the host, or inside each virtual
> machine?
suggestions for other groups! :)
Konrad Rzeszutek
I am not sure how you are partitioning your space. Does each guest
have an iSCSI target (or LUN) assigned to it? Or is it one big
drive that they run from? Also are you envisioning using this
with LiveMigration (or whatever it is called with your virtualization
system)?
Arturo 'Buanzo' Busleiman
> I am not sure how you are partitioning your space. Does each guest
> have an iSCSI target (or LUN) assigned to it? Or is it one big
> drive that they run from? Also are you envisioning using this
> with LiveMigration (or whatever it is called with your virtualization
> system)?
I'm using Vmware-Server (not ESX, just the free one).
The guests themselves (the disk where the OS is installed) are stored as
vmdk's on a local folder.
I want to provide application storage for each virtual machine, no
shared storage. I have 1.6TB total capacity, and plan on giving each
guest as much raid-5 storage space as they need.
The iscsiadm discovery on my Host reports all available targets, over
both interfaces (broadcom and intel).
So, basicly, I have these doubts / options:
1) Login to each target on the host, and add raw disk access to the
guests to those host-devices.
2) Don't use open-iscsi on the host, but use it on each guest to connect
to the targets.
And the main doubt: how does link aggregation / dualpath fit into those
options?
Also, i find this error:
root@VGEVS02:~# iscsiadm -m node -L all
Login session [iface: default, target:
iqn.1984-05.com.dell:powervault.6001e4f0004326c100000000482127e3,
portal: 192.168.130.102,3260]
Login session [iface: default, target:
iqn.1984-05.com.dell:powervault.6001e4f0004326c100000000482127e3,
portal: fe80:0000:0000:0000:021e:4fff:fe43:26c3,3260]
iscsiadm: initiator reported error (4 - encountered connection failure)
iscsiadm: Could not log into all portals. Err 107.
I'm using crossover cables.
Konrad Rzeszutek
>
> On May 28, 2:45 pm, Konrad Rzeszutek <kon...@virtualiron.com> wrote:
> > I am not sure how you are partitioning your space. Does each guest
> > have an iSCSI target (or LUN) assigned to it? Or is it one big
> > drive that they run from? Also are you envisioning using this
> > with LiveMigration (or whatever it is called with your virtualization
> > system)?
>
> I'm using Vmware-Server (not ESX, just the free one).
>
> The guests themselves (the disk where the OS is installed) are stored as
> vmdk's on a local folder.
>
> I want to provide application storage for each virtual machine, no
> shared storage. I have 1.6TB total capacity, and plan on giving each
> guest as much raid-5 storage space as they need.
>
> The iscsiadm discovery on my Host reports all available targets, over
> both interfaces (broadcom and intel).
>
> So, basicly, I have these doubts / options:
>
> 1) Login to each target on the host, and add raw disk access to the
> guests to those host-devices.
> 2) Don't use open-iscsi on the host, but use it on each guest to connect
> to the targets.
>
If you run iSCSI on each guests you end up with overhead. Each guests will
have to do its own iSCSI packet assembling/disassembling, along with doing
socket operations (TCP, IP assembling) and your target will X-Guests
connections. Each guest would need to run the multipath suite which puts
I/O on the connection every 40 seconds (or less if a failure has occurred).
If on the other hand you make the connection on your host, setup
multipath there, create LVMs and assign them to each your guests you have:
- less overhead (one OS doing the iSCSI packet assembling/disassembling),
TCP/IP assembling.
- one connection to the target. You can even purchase extra two NICs and
create your own subnet for them and the target so that there is no
traffic there (except iSCSI).
- one machine running multipath and you can make it queue I/O from
place if the network goes down. This will block the guests (you might
need to change the SCSI timeout in the guests - no idea what registry
key you need to change for this in Windows).
- One place to zone out your huge capacity and you can resize them
as you see fit from one place (using LVMs for guests and you can
re-size them).
> And the main doubt: how does link aggregation / dualpath fit into those
> options?
I can't give you an opinion about link aggregation as I don't have that
much experience in this field.
But in regards to multipath you are better of doing it on your host
than on the guest.
>
> Also, i find this error:
>
> root@VGEVS02:~# iscsiadm -m node -L all
> Login session [iface: default, target:
> iqn.1984-05.com.dell:powervault.6001e4f0004326c100000000482127e3,
> portal: 192.168.130.102,3260]
> Login session [iface: default, target:
> iqn.1984-05.com.dell:powervault.6001e4f0004326c100000000482127e3,
> portal: fe80:0000:0000:0000:021e:4fff:fe43:26c3,3260]
> iscsiadm: initiator reported error (4 - encountered connection failure)
> iscsiadm: Could not log into all portals. Err 107.
Did you configure your ethX to use IPV6? The second target IP
is in IPv6 format.
>
> I'm using crossover cables.
No switch? Then link-aggregation wouldn't matter I would think (since
the ARP requests aren't going to a switch).
>
>
> >
Mike Christie
open-iscsi does not really support link local ipv6 adders yet. There is
a way around this by setting up a iface for the net inerface (ethX) that
it is local to then binding it, but it is a little complicated to do.
Arturo 'Buanzo' Busleiman
> If you run iSCSI on each guests you end up with overhead.
I decided the same. So I'm running iscsi on the host, and via
/dev/disk/by-path/whatever provide the guests with SAN storage.
Bad thing there, for each virtual disk of the san, I get two /dev
entries, so I'm wondering how to setup the multipath over those two
/dev/disk/by-path entries (one over each controller).
I also noticed the IPv^ thing, so I ended up specifying the IP by hand,
and using to iscsiadm commands for each discovery / session initiation.
Also, as you said, link aggregation makes no sense over crossover and
two different interfaces.
What I'm NOT doing, is LVM. I wanted to go one layer at a time, and
adding LVM was too much for my limited time in here.
So, currently, I have two remaining issues:
1) setup multipath
2) **URGENT**: I've added a second virtual disk and mapped it to my host
(SAN is an MD3000i, host is ubuntu server with 2.6.24-17, i'm waiting
for 2.6.25 which fixes the skb broadcast bug it seems).
If I use hwinfo, I can see the virtual disk (over /dev/sdc and the 2nd
entry, /dev/sdf). Over fdisk, I get NOTHING.
Here's the dmesg output, hwinfo output, and fdisk output:
HWINFO
======
40: SCSI 300.1: 10600 Disk
[Created at block.222]
Unique ID: uBVf.EABbh0DH0_1
SysFS ID: /block/sdc
SysFS BusID: 3:0:0:1
SysFS Device Link: /devices/platform/host3/session1/target3:0:0/3:0:0:1
Hardware Class: disk
Model: "DELL MD3000i"
Vendor: "DELL"
Device: "MD3000i"
Revision: "0670"
Serial ID: "84L000I"
Driver: "sd"
Device File: /dev/sdc (/dev/sg4)
Device Files: /dev/sdc,
/dev/disk/by-id/scsi-36001e4f00043a3da000004dc4843982f,
/dev/disk/by-path/ip-192.168.131.101:3260-iscsi-iqn.1984-05.com.dell:powervault.6001e4f0004326c100000000482127e3-lun-1
Device Number: block 8:32-8:47 (char 21:4)
Geometry (Logical): CHS 102400/64/32
Size: 209715200 sectors a 512 bytes
Drive status: no medium
Config Status: cfg=new, avail=yes, need=no, active=unknown
That "drive status: no medium" drives me crazy. For comparison, this is
the output for the first virtual disk I created, the one I can access:
41: SCSI 300.0: 10600 Disk
[Created at block.222]
Unique ID: R0Fb.EABbh0DH0_1
SysFS ID: /block/sdb
SysFS BusID: 3:0:0:0
SysFS Device Link: /devices/platform/host3/session1/target3:0:0/3:0:0:0
Hardware Class: disk
Model: "DELL MD3000i"
Vendor: "DELL"
Device: "MD3000i"
Revision: "0670"
Serial ID: "84L000I"
Driver: "sd"
Device File: /dev/sdb (/dev/sg3)
Device Files: /dev/sdb,
/dev/disk/by-id/scsi-36001e4f0004326c1000005b3483e9c7a,
/dev/disk/by-path/ip-192.168.131.101:3260-iscsi-iqn.1984-05.com.dell:powervault.6001e4f0004326c100000000482127e3-lun-0
Device Number: block 8:16-8:31 (char 21:3)
Geometry (Logical): CHS 261/255/63
Size: 4194304 sectors a 512 bytes
Config Status: cfg=new, avail=yes, need=no, active=unknown
DMESG
=====
end_request: I/O error, dev sdc, sector 209715192
end_request: I/O error, dev sdc, sector 0
Buffer I/O error on device sdc, logical block 0
end_request: I/O error, dev sdc, sector 0
end_request: I/O error, dev sdc, sector 209715192
end_request: I/O error, dev sdc, sector 0
Buffer I/O error on device sdc, logical block 0
end_request: I/O error, dev sdc, sector 0
Buffer I/O error on device sdc, logical block 0
end_request: I/O error, dev sdc, sector 0
end_request: I/O error, dev sdc, sector 209715192
end_request: I/O error, dev sdc, sector 0
Buffer I/O error on device sdc, logical block 0
end_request: I/O error, dev sdc, sector 0
end_request: I/O error, dev sdc, sector 209715192
Buffer I/O error on device sdc, logical block 26214399
end_request: I/O error, dev sdc, sector 209715192
end_request: I/O error, dev sdc, sector 0
Buffer I/O error on device sdc, logical block 0
end_request: I/O error, dev sdc, sector 0
end_request: I/O error, dev sdc, sector 209715192
end_request: I/O error, dev sdc, sector 0
The attach-time messages got lost, but I remember this line:
Dev sdc: unable to read RDB block 0
FDISK
=====
root@vgevs01:~# fdisk -l /dev/sdc
root@vgevs01:~# fdisk /dev/sdc
Unable to read /dev/sdc
Might the disk still be initializing? The Dell client says it's finished...
Thanks!!
Konrad Rzeszutek
>
> On May 30, 10:29 am, Konrad Rzeszutek <kon...@virtualiron.com> wrote:
> > If you run iSCSI on each guests you end up with overhead.
>
> I decided the same. So I'm running iscsi on the host, and via
> /dev/disk/by-path/whatever provide the guests with SAN storage.
>
> Bad thing there, for each virtual disk of the san, I get two /dev
> entries, so I'm wondering how to setup the multipath over those two
> /dev/disk/by-path entries (one over each controller).
>
> I also noticed the IPv^ thing, so I ended up specifying the IP by hand,
> and using to iscsiadm commands for each discovery / session initiation.
That works. Bit of a hack. Why not just use the IPv4 on both interfaces?
> Also, as you said, link aggregation makes no sense over crossover and
> two different interfaces.
Well, you could use load balancing or play with ifaces with your two NICs
and take advantage of the two Ethernet cables from your target.
What this means is that you can setup the /dev/sdc to go over
one of your NICs, and the /dev/sdf over the other. For that look in
the README file and read up about ifaces. This is the poor man fine-grained
NIC configuration.
Or you can use load balancing where you bond both interfaces in one, but
for that you need a switch.. And the same for link aggregation or
link failure.
But as said before, you are doing cross-over so go with ifaces to
take advantage of setting up two sessions on both NICs.
>
> What I'm NOT doing, is LVM. I wanted to go one layer at a time, and
> adding LVM was too much for my limited time in here.
>
> So, currently, I have two remaining issues:
>
> 1) setup multipath
That is pretty easy. Just install the package and the two block devices
(or four if you are using a dual-controller) will be /dev/mapper/<some really
long UUID> on which you can use LVM.
> 2) **URGENT**: I've added a second virtual disk and mapped it to my host
> (SAN is an MD3000i, host is ubuntu server with 2.6.24-17, i'm waiting
> for 2.6.25 which fixes the skb broadcast bug it seems).
Huh? What skb broadcast bug?
> If I use hwinfo, I can see the virtual disk (over /dev/sdc and the 2nd
> entry, /dev/sdf). Over fdisk, I get NOTHING.
fdisk -l doesn't give you data?
Uh.. don't go crazy. Just install multipath and make sure you have this
configuration entry in mulitpath.conf file:
device {
vendor "DELL"
product "MD3000i"
product_blacklist "Universal Xport"
features "1 queue_if_no_path"
path_checker rdac
hardware_handler "1 rdac"
path_grouping_policy group_by_prio
prio "rdac"
failback immediate
}
Keep in mind that depending on what version of multipath you install
you might not have the 'rdac' path checker or that the path priority
program is called differently. Get the latest one and see what config
options you need.
(The above works with SLES10 SP2).
> the output for the first virtual disk I created, the one I can access:
>
> 41: SCSI 300.0: 10600 Disk
> [Created at block.222]
> Unique ID: R0Fb.EABbh0DH0_1
> SysFS ID: /block/sdb
> SysFS BusID: 3:0:0:0
> SysFS Device Link: /devices/platform/host3/session1/target3:0:0/3:0:0:0
> Hardware Class: disk
> Model: "DELL MD3000i"
> Vendor: "DELL"
> Device: "MD3000i"
> Revision: "0670"
> Serial ID: "84L000I"
> Driver: "sd"
> Device File: /dev/sdb (/dev/sg3)
> Device Files: /dev/sdb,
> /dev/disk/by-id/scsi-36001e4f0004326c1000005b3483e9c7a,
> /dev/disk/by-path/ip-192.168.131.101:3260-iscsi-iqn.1984-05.com.dell:powervault.6001e4f0004326c100000000482127e3-lun-0
> Device Number: block 8:16-8:31 (char 21:3)
> Geometry (Logical): CHS 261/255/63
> Size: 4194304 sectors a 512 bytes
> Config Status: cfg=new, avail=yes, need=no, active=unknown
>
That looks wrong. How many controllers do you have? I wonder if this is related to
the other session that didn't login. Have you set the LUN1 disk to have
a preferred controller which is the one using IPv6 and the LUN0 to use the
controller which is using IPv4?
Can you attach the output of 'iscsiadm -m session -P 3'? And the
iscsiadm -m discovery -t st -p 192.168.131.101
Nope. That just means you need to get the latest multipath code
to take advantage of your RDAC controller. The other block device
isn't activated and if you use multipath it will be accessible (well, kind of
. It will be a "passive" disk - meaning if the connection to the
active dies the I/O will switch over to the passive disk).
>
> Thanks!!
>
>
>
Bryan Mclellan
Bryan
http://blog.loftninjas.org/?p=195
Arturo 'Buanzo' Busleiman
I changed my setup to only initiate sessions to the primary domain
controller
. This is my dmesg output now:
[ 225.682760] sd 3:0:0:1: [sdc] 209715200 512-byte hardware sectors
(107374 MB)
[ 225.683124] sd 3:0:0:1: [sdc] Write Protect is off
[ 225.683129] sd 3:0:0:1: [sdc] Mode Sense: 77 00 10 08
[ 225.683856] sd 3:0:0:1: [sdc] Write cache: enabled, read cache:
enabled, supports DPO and FUA
[ 225.685255] sd 3:0:0:1: [sdc] 209715200 512-byte hardware sectors
(107374 MB)
[ 225.685640] sd 3:0:0:1: [sdc] Write Protect is off
[ 225.685644] sd 3:0:0:1: [sdc] Mode Sense: 77 00 10 08
[ 225.686757] sd 3:0:0:1: [sdc] Write cache: enabled, read cache:
enabled, supports DPO and FUA
[ 225.686763] sdc:end_request: I/O error, dev sdc, sector 0
[ 226.205534] Buffer I/O error on device sdc, logical block 0
[ 226.738010] end_request: I/O error, dev sdc, sector 0
[ 226.738018] Buffer I/O error on device sdc, logical block 0
[ 227.253843] end_request: I/O error, dev sdc, sector 0
[ 227.253850] Buffer I/O error on device sdc, logical block 0
[ 227.758117] end_request: I/O error, dev sdc, sector 0
[ 227.758124] Buffer I/O error on device sdc, logical block 0
[ 228.285522] end_request: I/O error, dev sdc, sector 0
[ 228.285530] Buffer I/O error on device sdc, logical block 0
[ 228.802647] end_request: I/O error, dev sdc, sector 0
[ 228.802654] Buffer I/O error on device sdc, logical block 0
[ 229.333818] end_request: I/O error, dev sdc, sector 0
[ 229.333823] Buffer I/O error on device sdc, logical block 0
[ 229.849659] end_request: I/O error, dev sdc, sector 0
[ 229.849664] Buffer I/O error on device sdc, logical block 0
[ 230.365489] end_request: I/O error, dev sdc, sector 0
[ 230.365495] Buffer I/O error on device sdc, logical block 0
[ 230.365561] Dev sdc: unable to read RDB block 0
[ 230.881333] end_request: I/O error, dev sdc, sector 0
[ 230.881339] Buffer I/O error on device sdc, logical block 0
[ 231.397134] end_request: I/O error, dev sdc, sector 0
[ 231.397139] Buffer I/O error on device sdc, logical block 0
[ 231.913060] end_request: I/O error, dev sdc, sector 24
[ 232.428813] end_request: I/O error, dev sdc, sector 24
[ 232.944649] end_request: I/O error, dev sdc, sector 0
[ 233.460491] end_request: I/O error, dev sdc, sector 0
[ 233.460580] sd 3:0:0:1: [sdc] Attached SCSI disk
[ 233.976394] end_request: I/O error, dev sdc, sector 0
[ 234.492213] end_request: I/O error, dev sdc, sector 0
[ 235.008043] end_request: I/O error, dev sdc, sector 0
[ 235.523861] end_request: I/O error, dev sdc, sector 0
[ 297.041718] end_request: I/O error, dev sdc, sector 0
[ 297.041728] Buffer I/O error on device sdc, logical block 0
[ 297.557553] end_request: I/O error, dev sdc, sector 0
[ 297.557561] Buffer I/O error on device sdc, logical block 0
[ 298.090022] end_request: I/O error, dev sdc, sector 0
[ 298.090031] Buffer I/O error on device sdc, logical block 0
[ 298.090094] Buffer I/O error on device sdc, logical block 1
[ 298.090166] Buffer I/O error on device sdc, logical block 2
[ 298.090222] Buffer I/O error on device sdc, logical block 3
[ 298.622514] end_request: I/O error, dev sdc, sector 0
[ 298.622521] Buffer I/O error on device sdc, logical block 0
[ 299.138350] end_request: I/O error, dev sdc, sector 209715192
[ 299.138358] Buffer I/O error on device sdc, logical block 26214399
[ 299.654205] end_request: I/O error, dev sdc, sector 209715192
[ 299.654214] Buffer I/O error on device sdc, logical block 26214399
[ 300.170001] end_request: I/O error, dev sdc, sector 0
[ 300.170009] Buffer I/O error on device sdc, logical block 0
[ 300.669786] end_request: I/O error, dev sdc, sector 0
[ 308.989195] end_request: I/O error, dev sdc, sector 0
[ 308.989205] Buffer I/O error on device sdc, logical block 0
[ 308.989280] Buffer I/O error on device sdc, logical block 1
[ 309.505007] end_request: I/O error, dev sdc, sector 0
[ 310.020849] end_request: I/O error, dev sdc, sector 209715192
[ 310.536690] end_request: I/O error, dev sdc, sector 209715192
[ 311.052532] end_request: I/O error, dev sdc, sector 0
[ 311.568367] end_request: I/O error, dev sdc, sector 0
[ 321.585585] end_request: I/O error, dev sdc, sector 0
[ 322.101500] end_request: I/O error, dev sdc, sector 0
[ 322.101509] Buffer I/O error on device sdc, logical block 0
[ 322.833613] end_request: I/O error, dev sdc, sector 0
[ 323.349434] end_request: I/O error, dev sdc, sector 0
[ 355.214898] end_request: I/O error, dev sdc, sector 0
[ 355.214905] Buffer I/O error on device sdc, logical block 0
[ 355.747385] end_request: I/O error, dev sdc, sector 0
[ 355.747394] Buffer I/O error on device sdc, logical block 0
[ 356.279864] end_request: I/O error, dev sdc, sector 0
[ 356.279873] Buffer I/O error on device sdc, logical block 0
[ 356.279935] Buffer I/O error on device sdc, logical block 1
[ 356.279996] Buffer I/O error on device sdc, logical block 2
[ 356.280051] Buffer I/O error on device sdc, logical block 3
[ 356.812357] end_request: I/O error, dev sdc, sector 0
[ 357.344816] end_request: I/O error, dev sdc, sector 209715192
[ 357.344826] Buffer I/O error on device sdc, logical block 26214399
[ 357.877276] end_request: I/O error, dev sdc, sector 209715192
[ 358.409751] end_request: I/O error, dev sdc, sector 0
[ 358.942231] end_request: I/O error, dev sdc, sector 0
Apparently, no changes, except that there are no partitions sde through sdg.
hwinfo and fdisk still report the same.
Btw, I also removed the Access DellUtility partition. No difference
either, except that /dev/sdd disappeared :)
Any other ideas?
Bryan Mclellan
I'd make sure you can ping all of the nodes (four if you have two controllers).
Discover them all via sendtargets and log in to all of them.
iscsiadm -m discovery -t st -p 192.168.130.101
iscsiadm -m node -l
fdisk -l
You should end up with two or four devices (depending on number of controllers); one for each virtual disk mapped to that host for each node you've logged in to, provided you've removed the Access mapping, which should be just fine. Fdisk -l should print a partition table, or lack thereof, for all the disks it can read (which should be half of number of nodes)
It took me a while to figure out that I couldn't access the disks via the second controller and playing around with iscsiadm a lot is what finally clued me in to it. It helped that I already had a test partition on the virtual disk created elsewhere so cat '/proc/partitions' revealed that the partition was only visible on two of the disk devices not all four.
Bryan
As a side note, I'd double check your subnet configurations on the controllers. Each controller should only have one interface on a specific subnet. I don't think this is related to your current problem though.
-----Original Message-----
From: open-...@googlegroups.com [mailto:open-...@googlegroups.com] On Behalf Of Arturo 'Buanzo' Busleiman
Sent: Monday, June 02, 2008 12:08 PM
To: open-...@googlegroups.com
Subject: Re: Problems accessing virtual disks on MD3000i, was: RE: Design Questions
Hi Bryan,
I changed my setup to only initiate sessions to the primary domain
controller
. This is my dmesg output now:
<snip>
Arturo 'Buanzo' Busleiman
BANG, the host SAW it with no problems whatsoever.
Maybe 100gb and/or lun-1 makes any difference? i hope not!
Buanzo,
a very puzzled man.
Konrad Rzeszutek
> hwinfo and fdisk still report the same.
>
> Btw, I also removed the Access DellUtility partition. No difference
> either, except that /dev/sdd disappeared :)
>
> Any other ideas?
multipath-tools? Did you install it?
Arturo 'Buanzo' Busleiman
> OK, don't ask me why, but I just added a 20gb virtual disk on LUN-3,
> and BANG, the host SAW it with no problems whatsoever.
>
> Maybe 100gb and/or lun-1 makes any difference? i hope not!
and put the disk I couldn't access on one of the two controller ports I
see on this server.
I guess moving from a cross-over cabling to a switched solution is what
I'll do next. (and setup multipath).
Buanzo.
Eli Dorfman
> a way around this by setting up a iface for the net inerface (ethX) that
> it is local to then binding it, but it is a little complicated to do.
>
When do you think ipv6 will be supported? what needs to be done?
Thanks,
Eli
Mike Christie
>> open-iscsi does not really support link local ipv6 adders yet. There is
>> a way around this by setting up a iface for the net inerface (ethX) that
>> it is local to then binding it, but it is a little complicated to do.
>>
> Can you explain in details how to do that.
Ok not that complicated. Just bind to a iface like you would normally.
Setup a iface and bind it do the ipv6 link local portal that was
discovered by doing:
iscsiadm -m node -T target -p your_ipv6_link_local_addr -I
iface_you_created_that_can_access_ipv6_link_local_portal -o new
then login like normal.
the problem is that you cannot do discovery to a link local addr though.
> When do you think ipv6 will be supported? what needs to be done?
>
I have no plans to support ipv6 link local addrs. You need some code to
tell it what network interface to use or maybe loop over every network
interface and figure out which one to use for the user.