R-Barrier: Rapid Barrier for Software RAID Cache Using Hints From Journaling Filesystem
While adopting cache in software RAID brings performance benefit, it can cause data loss at power failure which results in the broken file-system consistency. Though I/O Barrier can be used to remove the consistency issue, it sacrifices the write performance of software RAID. To mitigate this tradeoff, the authors suggest R-Barrier for software RAID. The basic idea of R-Barrier is to avoid the synchronization of the entire cache space. Instead, based on given hints from the file-system layer, R-Barrier makes software RAID cache select one of the following methods when the cache writes a certain write request into the disk: strictly ordered destaging for the write requests affecting the file-system consistency; reordered destaging for the rest of write requests.