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I can put together two linux servers and use the (more or less) new DRBD dual-primary feature to get a shared block device with concurrent read/write access on the two nodes.

Can I then export an iSCSI target from each node and use the two like a single multipath iSCSI device? eg. to simulate a dual-controller iSCSI storage array

I know I can work on both nodes via iSCSI, I just don't know if the multipath thing needs any knowledge about it from the two targets or if they are completely independent and without shared state as long as iSCSI is concerned.

(NB I'm not going to use such a setup in production, it would be just a testbed replacement for a true dual controller iSCSI array that we don't own yet. I'm gonna connect a server to both targets and test the multipath'ing by disconnecting one of the two links)

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Ok that was easy enough to make me feel stupid for not finding it with google in the first place.

Short answer: no

Better answer: as people from the iSCSI Enterprise Target mailing list told me, this has been already discussed in the past and is not possible with current implementations, because the two iSCSI targets would need to have some shared state and talk to each other. This feature per se has not been implemented in any linux iSCSI target, and most probably it won't ever. This is because the main (only?) useful use case is in conjunction with DRBD and if its data path between the two nodes gets interrupted we would need really fast and really hard fencing of one node (details in the linked blog entry).

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