Intel AFCSASRISER User Guide - Page 44

• SMART (Self-Monitoring Analysis and Reporting Technology) technology is supported. This provides a higher level of predictive failure analysis of the hard disk drives by the RAID controller. Cache Options and Settings Cache options and settings can be unique for each virtual drive. • Cache Write Policy - Write Through: I/O completion is signaled only after the data is written to hard disk. - Write Back with BBU: I/O completion is signaled when data is transferred to cache. - Always Write Back- Write back is enabled even if BBU is bad or missing • Cache Policy - Direct I/O: When possible, no cache is involved for both reads and writes. The data transfers are directly from host system to the disk and from the disk to the host system. - Cached I/O: All reads first look at cache. If a cache hit occurs, the data is read from cache; if not, the data is read from disk and the read data is buffered into cache. All writes to drive are also written to cache. • Read Policy - No Read Ahead: Provides no read ahead for the virtual drive. - Read Ahead: Reads and buffers additional consecutive stripes/lines into cache. - Adaptive: The read ahead automatically turns on and off depending upon whether the disk is accessed for sequential reads or random reads. Background Tasks • Rebuilding a failed drive is performed in the background. The rebuild rate is tunable from 0-100%. - The rebuild rate controls the amount of system resources allocated to the rebuild. Caution: It is not recommended to increase the rebuild rate to over 50%. A higher rebuild rate can result in operating system requests not being serviced in a timely fashion and causing an operating system error. • A consistency check scans the consistency of data on a fault-tolerant disk to determine if data has been corrupted. • Background initialization is a background check of consistency. It has the same functionality as the check consistency option but is automatic and can be canceled only temporarily. If it is canceled, it starts again in a few minutes. Background initialization is only performed on redundant volumes. • RAID level migration and online capacity expansion are completed in the background. • Patrol Read is a user definable option available in the Intel® RAID Web Console 2 that performs drive reads in the background and maps out any bad areas of the drive. 32 Intel® RAID Software User's Guide