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How should one connect a small storage array, four 3TB SATA drives for now, to two motherboards or controllers as a failover system? This means avoiding adding another single point of failure such as a single SAN device. A perfect world would have a [non-RAID] controller on an expansion card (PCIe, PCIX) made for exactly this task, or have the capability built into common motherboards.

I'm avoiding hardware RAID cards as this is just a backup solution, not a high performance server, and will be implementing ZFS (RAID-Z2, similar to RAID-6).

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Seems odd you'd consider having redundant motherboards without redundant storage for a data replica of any sort - yet with what you propose, dispense with the idea of a SAN/NFS? Is money the rationale? You discuss a motherboard specifically, do you actually mean a full host (CPU, memory, etc) - sans drives? – thinice Jan 16 '12 at 0:46
The storage black has redundancy, @thinice. ZFS (RAID-Z2) has similar disk failure tolerance to RAID-6. – tyblu Jan 16 '12 at 0:51
@thinice, I mean a motherboard with CPU and memory (and possibly controller card). – tyblu Jan 16 '12 at 0:54
up vote 5 down vote accepted

You can't. Sata is a one-to-one connection. Even in San setups with multiple paths to multiple servers there is always a single point of failure which is dealt with by having multiple arrays.

There are multiple ways you can make that storage available to multiple servers eg. a NAS, but you are just moving the single point of failure around.

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So that's why it's so hard to find these magical controllers. – tyblu Jan 16 '12 at 1:14
SAS drives can have multiple ports, which could be connected to multiple backplanes (in practice I've never seen this, it's always a single backplane), multiple controllers, etc back to the server(s). You are correct however that SATA doesn't support any such mechanism. – Chris S Jan 16 '12 at 1:18

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