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We've always used DAS storage (which as per Dell standards) have multiple controllers for redundancy, multiple PSUs etc. However, in the event of full hardware failure (which may or may not be likely) something like DAS replication would be the obvious answer.

However, how would that tie into clusters. Say a Hyper-V cluster utilising CSVs on a DAS, if that entire DAS failed, how would the replicated DAS take over, is this even possible?

Would you need a seperate cluster running copies of the VMs on a DAS setup with DAS replication to achieve this? What would be the best approach?

PnP
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1 Answers1

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DAS is really intended as a local storage extension for standalone machines. The availability of DDAS (DASD) boxes, that allow more than one host access to the VDs (Dell term) in them is really a poor man's SAN, with some very harsh limitations. So really, what you need to be looking at is SAN replication in DR scenarios.

Having said that, the Dell PV boxes have no replication at all (unless you use software in the host to replicate the volumes, like DRBD), and the higher end MDs aren't really a DAS, even those that have SAS connectors.

Having said all that, a typical replicated storage DR scenario means a complete site failure, where the hosts and the SAN are down, and a remote site, where everything was replicating to has to pick up the load. In this case failover is usually manual (to avoid SB and in general, a DR scenario is not something to take lightly and let automation do the job). What happens is the hosts are brought up at the DR site, connected to the DR SAN, where they pick up the replicated VMs, and start them. Obviously there's much more (like the changes in networking, DNS etc) but that's the general idea.

Local SAN redundancy is usually achieved with simpler means - multipathing, fabric redundancy (several fabric switches), RAID, redundant controllers and PSUs, redundant HBAs in the hosts. Obviously most of this will not be available with basic not-quite-SAN SAS attached devices like the entry level MD3xxx (sans the -i or -f)

dyasny
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