Re: [Xen-users] Safe iSCSI & Live Migrations

[Tom Brown <xensource.com@xxxxxxxxxxxxxxxxxxx>]

> You're quite correct, Dom0 is exporting block devices to the DomUs.  I was 
> trying to keep iSCSI out of the DomU's, but maybe in the end that is the 
> easiest way to achieve safe iSCSI with Live Migrations.
> A description of what may be involved with booting off iSCSI directly from 
> within a DomU can be found here [1].  It looks like the author had to hard 
> code the iSCSI configuration in the custom initrd.img, and change it for each 
> DomU.
There shouldn't be a need to burn basic connection parameters
into your initrd files. The init file can pick up environment
variables from the kernel command line.  I used this when I was 
testing root on nbd and gnbd  configurations ...
Which is to say I had the following in my domU config file (on
one line)
extra="NBDHOST=192.168.97.90 NBDPORT=8001
   ip=192.168.97.91:1.1.1.1:192.168.97.254:255.255.255.0"

I had to "break open" one of my old initrd files to extract this, but
it was working :)

<snip>

#TAB
#/bin/nbd-client host port nbd_device
# The following assumes we have NBDHOST=1.2.3.4 and NBDPORT=8001
# as kernel parameters
# we also need the network interface to be configured via:
# ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>

/bin/nbd-client $NBDHOST $NBDPORT /dev/nbd0  -persist

<snip>

I'm now using aoe on a second ethernet interface (eth1) which is
pretty simple, assuming udev works right ... and if it doesn't
it's not that big a deal to build the /dev/etherd devices in your
initrd.

(and yes, I'm a fan of pushing the domU network disk logic into the domU, 
both to keep dom0 simple/stable and to allow easy migrations.)
-Tom


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