Apparatus, system, and method for preventing write starvation in a partitioned cache of a storage controller

An apparatus to prevent write starvation in a storage controller with access to low performance storage devices, the apparatus comprising:

• a storage device allocation module configured to assign a storage device write cache limit for each storage device accessible to a storage controller, the storage device write cache limit comprising a maximum amount of write cache of the storage controller available to a storage device for a write operation, wherein at least one storage device comprises a low performance storage device and a total amount of storage available to the storage devices comprises an amount greater than a total storage capacity of the write cache;
• a low performance write cache limit module configured to set a low performance write cache limit, wherein the low performance write cache limit comprises a total amount of write cache available for use by low performance storage devices for write operations, wherein the amount of write cache available to the low performance storage devices comprises an amount less than the total storage capacity of the write cache;
• a request module configured to receive a request to store an update to a low performance storage device;
• a write cache storage module configured to store the update in the write cache in response to
• the size of the update plus an amount of the write cache occupied by updates ready to be written to the low performance storage device being less than or equal to the storage device write cache limit;
• and
• the size of the update plus an amount of the write cache occupied by updates ready to be written to the low performance storage devices accessible to the storage controller being less than or equal to the low performance write cache limit;
• and
• a destage module configured to destage the update to the low performance storage device.

A system to prevent write starvation in a storage controller with access to low performance storage devices, the system comprising:

• a plurality of storage devices, wherein at least one of the storage devices comprises a low performance storage device;
• and
• a storage controller connected to the plurality of storage devices, the storage controller comprising
• a storage device allocation module configured to assign a storage device write cache limit for each storage device accessible to the storage controller, the storage device write cache limit comprising a maximum amount of write cache of the storage controller available to a storage device for a write operation, wherein at least one storage device comprises a low performance storage device and a total amount of storage available to the storage devices comprises an amount greater than a total storage capacity of the write cache;
• a low performance write cache limit module configured to set a low performance write cache limit, wherein the low performance write cache limit comprises a total amount of write cache available for use by low performance storage devices for write operations, wherein the amount of write cache available to the low performance storage devices comprises an amount less than the total storage capacity of the write cache
• a request module configured to receive a request to store an update to a low performance storage device;
• a write cache storage module configured to store the update in the write cache in response to
• the size of the update plus an amount of the write cache occupied by updates ready to be written to the low performance storage device being less than or equal to the storage device write cache limit;
• and
• the size of the update plus an amount of the write cache occupied by updates ready to be written to the low performance storage devices accessible to the storage controller being less than or equal to the low performance write cache limit;
• and
• a destage module configured to destage the update to the low performance storage device.