We are planning a replicated cluster. Due to a combination of purchasing cycles, floor loading and VAT-exemption status for half the equipment/data, this will be built over time using a total 8 Lenovo DSS building blocks. 2 main pools, in 2 data centres, with 2 DSSG per pool, and a quorum/manager node with a local tie breaker disk in a 3rd physical location.
My main question is about failure groups - so far, with 2 DSS and 1 tiebreaker, we would have had 1 failure group per DSS and 1 for the tie breaker disk, giving us a total of 3. But if we did that now we would have 9 failure groups in 1 filesystem, which is more than the maximum number of replicas of the file system descriptor and not desirable, as I understand it. So we could have either: * 1 FG per physical site, and assign all 4 DSS per site to 1 FG, and a 3rd to the tiebreaker * 1 FG per pool per site, with 2 DSS in each FG. This makes sense as the pairs of DSSG will both always need to be up for all the data in the pool to be accessible. The second option would give us 5 failure groups, but what would be the advantage and disadvantages of more failure groups? Many thanks, Luke -- Luke Sudbery Principal Engineer (HPC and Storage). Architecture, Infrastructure and Systems Advanced Research Computing, IT Services Room 132, Computer Centre G5, Elms Road Please note I don't work on Monday.
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