Netapp, Inc.

Network Appliance, Inc.

Chris A Busick

William D Dallas

Edward Barron

Jan Reimers

An indication of an event is received at a storage controller. The indication of the event corresponds to a first severity. It is determined that the event is associated with a first stream of commands. It is determined whether the indication of the event is the first indication of the event received by the storage controller. If the indication of the event is the first indication of the event received by the storage controller, a maximum allowed count of in-flight commands to be less than a current count of in-flight commands is set. If the indication of the event is not the first indication of the event received by the storage controller, it is determined that the first severity is greater than a second severity corresponding to a previously received indication. If the first severity is greater than the second severity, the maximum allowed count of in-flight commands is decreased.

In-flight command queue depth management

An indication of an event occurrence is received. The indication of the event occurrence is associated with a severity. A tag associated with the indication of the event occurrence is determined. It is determined whether the tag is the same as a preceding tag. In response to a determination that the tag is not the same as the preceding tag, a component is notified of the event occurrence, the tag is stored for later use, and an indication of the severity associated with the indication of the event occurrence is stored.

Event based tagging of storage system commands

Method and system for handling error events on a current path for processing an I/O request for reading information from and writing information to a storage space is provided. A system is able to communicate with the storage space via more than one path. If the current path reports an error event, then an alternate path quality is determined to ascertain whether the alternate path will generate an error similar to the current path. The alternate path quality is determined based on a plurality of factors which are assigned certain weights. The weights are determined based on a likely contribution of each factor to a repetition of the error reported by the current path. If the alternate path quality is equal to or exceeds a programmable threshold value, then the alternate path is selected.

Method and system for path selection in a network

Lun communications between a storage server and a storage subsystem for a particular lun are assigned both a current path and an alternate path. Lun communications use the current path unless the current path is determined to be faulty. Path errors may result in the storage server determining a path to be faulty. If the current path for a lun communication is determined to be faulty, then the lun communications will be sent through the alternate path so long as the alternate path is determined to be reliable. Over time, a path previously determined to be faulty may recover and be used again for lun communications.

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Shrewsbury, MA, United States of America

Chris A Busick