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I have some Adaptec SAS raid controllers and the fanout cable comes with an extra cable called a SideBand but I am curious what it does?

I know it plugs into the backplane, but other than that I can't seem to find anything on google

The adaptec site refers to it as "SFF-8448 sideband signals" and there is no mention of it in the manuals or their site.

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up vote 5 down vote accepted

The sideband cables are used to connect the controller to a managed backplane or disk enclosure, so that it can monitor the controller as well as the disks.

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That's kind of obvious, I have figured that out. But what specifically does it do? Thanks. – Chad Grant May 7 '09 at 9:36
It lets the backplane monitor the status of the Raid controller and send alerts should there be a problem. What else do you want to know ? The specifics of how it talks to the controller? – Sam May 7 '09 at 9:58

This PDF document "SFF-8448 Specification for SAS Sideband Signal Assignments", (Rev. 05; September 2, 2005) on Seagate's FTP Server defines the signal assignments for known Vendor specific sidebands thata are defined in SAS (Serial Attached SCSI).

On page 12 there is a description of the Sideband Assignments.

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