Hello all,

  A couple of months ago I wrote up some ideas about clustered
ZFS with shared storage, but the idea was generally disregarded
as not something to be done in near-term due to technological

  Recently I stumbled upon a Nexenta+Supermicro report [1] about
cluster-in-a-box with shared storage boasting an "active-active
cluster" with "transparent failover". Now, I am not certain how
these two phrases fit in the same sentence, and maybe it is some
marketing-people mixup, but I have a couple of options:

1) The shared storage (all 16 disks are accessible to both
   motherboards) is split into two ZFS pools, each mounted
   by one node normally. If a node fails, another imports
   the pool and continues serving it.

2) All disks are aggregated into one pool, and one node
   serves it while another is in hot standby.

   Ideas (1) and (2) may possibly contradict the claim that
   the failover is seamless and transparent to clients.
   A pool import usually takes some time, maybe long if
   fixups are needed; and TCP sessions are likely to get
   broken. Still, maybe the clusterware solves this...

3) Nexenta did implement a shared ZFS pool with both nodes
   accessing all of the data instantly and cleanly.
   Can this be true? ;)

If this is not a deeply-kept trade secret, can the Nexenta
people elaborate in technical terms how this cluster works?

[1] http://www.nexenta.com/corp/sbb?gclid=CIzBg-aEqKwCFUK9zAodCSscsA

//Jim Klimov
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