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Re: How to hot swap an SCA SCSI disk with NetBSD
>> SCA is just a type of connector. As far as I know, there are no
>> extra signals (in particular there is no way to signal the OS that
>> the device was removed).
> That's true, but, generally, SCA backplanes are intelligent devices
> which can report device insertion/removal to the host over the SCSI
> bus - see ses(4).
The backplane still has to notice it somehow.
Also, "generally" is, I suspect, an artifact of the hardware you've
worked with. Most of my SCA equipment is not that smart - the SS20,
for example, uses SCA but has nothing of the sort as far as I can tell.
To get back on the original subthread, I wouldn't want to connect or
disconnect a load from a bus that's got live operations going on it;
for hot-swap, I'd expect switching electronics that does the
disconnect/reconnect before/after the electrical contact is
broken/made, and timed to not disrupt a transfer in progress. Either
that or I'd use bidirectional buffer logic, so there is nothing like a
direct electrical connection between the SCA pins and the SCSI bus.
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