HAST: more than one remote nodes, is it possible?

[Mikolaj Golub]

Hi,

So is it possible to have several remote (secondary) nodes with HAST? Although
current version of hastd supports only one remote node, it looks like it is
possible building HAST devices in stack :-)

I tried this under VirtulBox and it worked for me.

Having 2 pairs of hosts I built lower HAST devise on both pairs and then upper
resource using lower as a provider for upper. Any host can be used as primary
for upper in this configuration. To make things more interesting I installed
jail (VIMAGE) on upper device so vm can be moved between 4 hosts.

Below is hast.conf:

----------------------------------------------------------------------

# Stacked HAST -- data are written to 4 nodes (lolek, bolek, chuk and
# gek) and are accessible on one of the nodes as /dev/hast/upper
#
# /dev/hast/upper
#        |
#        P------------upper-------------S
#        |         172.20.68.30         |
# /dev/hast/lower                /dev/hast/lower
#        |                              |
#        P-----lower----S               P----lower-----S
#        | 172.20.68.31 |               | 172.20.68.32 |
#     /dev/ad4       /dev/ad4        /dev/ad4       /dev/ad4
# 
#      lolek          bolek            chuk           gek

exec /etc/vip.sh

resource lower {

	local /dev/ad4

	on lolek {
		remote bolek
	}

	on bolek {
		remote lolek
	}

	on chuk {
		remote gek
	}

	on gek {
		remote chuk
	}
}

resource upper {

	local /dev/hast/lower
	# XXX: HAST should be patched to know friends 
	friends lolek bolek chuk gek

	on lolek {
		remote 172.20.68.32
	}

	on bolek {
		remote 172.20.68.32
	}

	on chuk {
		remote 172.20.68.31
	}

	on gek {
		remote 172.20.68.31
	}
}

----------------------------------------------------------------------

As it is noted in the comments above hastd should be patched: current version
of hastd allows only connections from addresses specified as remote. The patch
is attached.

/etc/vip.sh is used to switch IP addresses between hosts.

Details can be found here:

http://code.google.com/p/hastmon/wiki/StackedHAST

-- 
Mikolaj Golub

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