System and method for improving I/O performance by introducing extent pool level I/O credits and user I/O credits throttling on Mapped RAID

A computer program product residing on a non-transitory computer readable storage medium having a plurality of instructions stored thereon which, when executed across one or more processors, causes at least a portion of the one or more processors to perform operations comprising:

• receiving an Input/Output (I/O) request for data;
• determining a number of storage devices of a plurality of storage devices in a Mapped Redundant Array of Independent Disks (RAID) group that will be used to process the I/O request, wherein determining the number of storage devices includes breaking down the received I/O request into a number of disk I/O credits via a Mapped RAID object and determining an amount of the number of disk I/O credits involved for processing the I/O request, wherein a capacity of space of the Mapped RAID group is exposed to a cache through a Flare LUN (FLU) such that when the I/O request is sent to the cache, a user I/O sends the I/O request to the FLU where the Mapped RAID group breaks the I/O request into a set of disk extents;
• determining that each storage device of the number of storage devices in the Mapped RAID group that will be used to process the I/O request lacks a respective threshold number of I/O credits to process the I/O request, wherein an I/O credit represents an I/O operation on a storage device of the plurality of storage devices in the Mapped RAID group, wherein determining that each storage device of the number of storage devices in the Mapped RAID group lacks the respective threshold number of I/O credits includes calculating, for the user I/O via an associated RAID object, which disk position I/O is capable of at least one of accessing and requesting the number of disk I/O credits together with the I/O credit;
• determining whether the cache associated with the Mapped RAID group allows a user I/O queue in response to determining that each storage device of the number of storage devices in the Mapped RAID group that will be used to process the I/O request lacks the respective threshold number of I/O credits;
• if the cache allows the user I/O queue, placing the user I/O in the user I/O queue;
• and
• if the cache does not allow the user I/O queue, failing the I/O request.

A computing system including one or more processors and one or more memories configured to perform operations comprising:

• receiving an Input/Output (I/O) request for data;
• determining a number of storage devices of a plurality of storage devices in a Mapped Redundant Array of Independent Disks (RAID) group that will be used to process the I/O request, wherein determining the number of storage devices includes breaking down the received I/O request into a number of disk I/O credits via a Mapped RAID object and determining an amount of the number of disk I/O credits involved for processing the I/O request, wherein a capacity of space of the Mapped RAID group is exposed to a cache through a Flare LUN (FLU) such that when the I/O request is sent to the cache, a user I/O sends the I/O request to the FLU where the Mapped RAID group breaks the I/O request into a set of disk extents;
• determining that each storage device of the number of storage devices in the Mapped RAID group that will be used to process the I/O request lacks a respective threshold number of I/O credits to process the I/O request, wherein an I/O credit represents an I/O operation on a storage device of the plurality of storage devices in the Mapped RAID group, wherein determining that each storage device of the number of storage devices in the Mapped RAID group lacks the respective threshold number of I/O credits includes calculating, for the user I/O via an associated RAID object, which disk position I/O is capable of at least one of accessing and requesting the number of disk I/O credits together with the I/O credit;
• determining whether the cache associated with the Mapped RAID group allows a user I/O queue in response to determining that each storage device of the number of storage devices in the Mapped RAID group that will be used to process the I/O request lacks the respective threshold number of I/O credits;
• if the cache allows the user I/O queue, placing the user I/O in the user I/O queue;
• and
• if the cache does not allow the user I/O queue, failing the I/O request.