Triple backplane – discrepancy between Redbook vs offical doc
January 10, 2014
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In a Redbook I found a pretty serious discrepancy about disk drive location, if you run a triple split backplane.The Redbook “IBM REDP-4924-00” chapter 2.9.2 describes a scenario with three SAS controllers. On page 83 you can find following picture
According to the Redbook the SAS controllers located on a backplane operates first two disks in horizon order SAS1(D1-D2), SAS2 (D4-D6), and the an additional SAS adapter controls last two disks in vertical order (D3-D6).
But the official technical documentation shows that all SAS adapters controls disks in vertical order here
When I was about to move configuration from two-way to triple way backplane, I really afraid which document is correct.
In the end, the official document is correct.
This misleading Redbook information might have serious consequence with potentially impacting user data. If a user run a mirror between disks, he doesn’t know if disks are going to be a part of SAS1 or SAS2 configuration.
I’m going to inform the Redbook authors