Feature #12971

SES nodes could be supported by vhci symmetric fops

Added by Garrett D'Amore 3 months ago. Updated 3 months ago.

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driver - device drivers
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SES devices are generally idempotent and stateless -- i.e. there is not normally an ordering constraint between operations.

Initial testing has shown that given a change made to the sym fops module to automatically include SES (DTYPE_ESI) devices (excluding those with explicit TPGS claims, which we have seen before - 3PAR), they can work well with mpxio.

Having SES nodes serviced by mpxio brings easier administration when multiple paths are present, allows them to be surfaced and managed via mpathadm, and gives consuming applications a simpler surface to work with as they no longer need to worry about dealing with resolving partial failure caused by loss of a redundant path. The mpxio framework already does an excellent job of this, and we should just make use of that.


Updated by Robert Mustacchi 3 months ago

Is there a way to make sure that the non-idempotent and ordering-dependent operations like downloading firmware with partial updates still behave in a deterministic way? Take he example of SEND DIAGNOSTIC for Microcode Download. Is it correct that in this case the design here is that the issuer is only issuing one command at a time, even if multiple SEND DIAGNOSTICS are required, and that the path doesn't matter? Given that the same is probably true for normal devices, I imagine it's likely the same for SES.

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