OFFLOADING RAID UPDATE OPERATIONS TO DISK CONTROLLERS

摘要

An improved technique involves performing computations for partial stripe updates in a RAID at individual disk controllers rather than at the RAID controller. When a RAID controller receives a request to update old payload data at a block in a particular disk with update data, it sends the update data to the controller of that particular disk. The disk controller reads internally old data from the block, computes the difference between new and old data, replaces the old data on disk with the new data, and returns the difference to the RAID controller. The RAID controller computes difference values of the parity data from the difference values of the payload data received from the disk controllers. It then sends these difference values to the controllers of disks storing parity data. A controller of a disk storing parity data reads internally the corresponding data block, adds to it the difference value, and writes the result back to disk.

主权项

1. In a storage system including a redundant array of disks having an array controller, each disk of the redundant array of disks including a disk controller apart from the array controller, a method of updating data stored on the redundant array of disks, the method comprising:
receiving, by the disk controller of a particular disk of the redundant array of disks, a request to update particular data stored in a block on the particular disk, the request including an input value; reading, by the disk controller of the particular disk, the particular data from the block on the particular disk; performing, by the disk controller of the particular disk, an update operation on the particular bit data stored in the block on the particular disk, the update operation including a swapping operation involving the particular bit data and the input value and serving to produce an update result; and writing, by the disk controller of the particular disk, the update result to the block on the particular disk.