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3 Host VMware Bundle and SAN

Posted on 2013-11-05
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Last Modified: 2013-11-06
Hi. Our organization is looking into the 3 Host VMware Bundle and SAN for virtualizing our servers.  Our sales rep. says if one of the 3 Hosts went down the VMs will be distributed across the remaining two Hosts. The rep. says this is achieved through the SAN. When we asked, what if the SAN failed instead of the 3 Hosts, the rep. gave us an uncomfortable answer. The rep. says there are a number of redundancy built into the SAN. We are not trying to be smart with the rep. but when we asked, what if the one and only single backplane in the SAN dies, the rep. doesn't seem to have an answer except recommending a spare SAN on standby. Can you please share your expertise on generally what is stored on the SAN and what are our risks if the SAN dies (i.e. what if a non redundant component of a SAN failed) ?  Thanks!
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Question by:COCO3515
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Andrew Hancock (VMware vExpert / EE MVE^2) earned 400 total points
ID: 39625613
Firstly, when using VMware HA in a Cluster of three hosts, if a host should fail due to unexpected failure, it's true after 1-2minutes of downtime, the HA Agents on the Hosts will restart the failed VMs on the remaining Hosts.

Providing that all the virtual machines are stored on the SAN.

If you have a SAN failure, ALL Virtual Machines are DOWN and not available. Yes, this does happen, when you have a single point of failure as a single SAN.

Options:-

1. Two SANs
2. SAN replication (between Two SANs)
3. Clustered Heads e.g. NetApp Filers
4. Clustered SANs e.g. HP LeftHand or VSA, or VMware vSphere VSA
(the above are two SANs which are clustered nodes, so data is mirrored between SANs, if a node fails, the SAN is still up)
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by:paulsolov
paulsolov earned 100 total points
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The SAN is a SPOF (Single Point of Failure) but it is a high availability SPOF.  Depending  on how you want to define your environment the datacenter can be considered a SPOF

That said the SAN usually has redundancy on the controllers, cabling, power, etc..  Unless you have a budget for another SAN and replication onsite then you have to pick your battles and take the pros and cons of any configuration.
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