We want to make a SAN with spare hardware we have in our shop just to use for cluster testing/training. Is there a poor man's way to create a SAN to be used for this purpose?


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Yup, and you don't even need a SAN at all to test clustering. You can create a shared SCSI cluster. I assume your servers are currently connected to some sort of an external disk shelf or shelves. You can share those disks within a cluster environment by simply connecting both servers to the same SCSI drive shelf.

To do this, you will need to purchase two external SCSI terminators, and two SCSI "Y" adapters. You place the terminators on one end of each Y adapter, connect the other end of each Y cable to the other via female-to-female extension cable then, connect the bottom part of each Y to the external SCSI connector on each server. You will have to reset the SCSI IDs on the controller in each server to be Unique with one being at ID7 and the other at ID6. Your drives should be set to 0-6. It should look something like this:

This is the setup I used to use when I worked with the original NT cluster solutions at Digital Equipment Corp, using HSZ70 SCSI disks and Adaptec SCSI controllers. This was actually a supported configuration from Microsoft for MSCS. This solution may also work with Unix clustering but you should check with your cluster software vendor.

For a poor man's SAN you will need a disk shelf that supports Fibre Channel and a single HUB. You can use older LP7000 Emulex adapters in the servers, which support the FC-AL protocol, and should be fairly cheap these days if you can still find them. You can also use two HBAs and two Hubs to test for fault tolerance. The solution should look something like this:

I'd like to thank my friends who gave me these pretty diagrams during my days at Digital. For your solution, you would just need one storage shelf, one HBA per server and one hub.

Hope this helps.

Chris

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This was first published in September 2003

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