1. A method comprising: receiving, at an input/output (I/O) adapter in a microserver chassis comprising a plurality of compute nodes and a shared storage resource, policy contexts prescribing storage access parameters of respective compute nodes; enforcing, at the I/O adapter, the respective policy contexts on I/O operations by the compute nodes, wherein a particular I/O operation by any compute node is not executed when the respective policy context does not permit the particular I/O operation; allocating tokens to command descriptors associated with I/O operations for accessing the shared storage resource; identifying, at the I/O adapter, a violation of any policy context of any compute node based on availability of the tokens; and throttling I/O operations by other compute nodes until the violation disappears.