Intel AXXROMBSASMR Hardware User Guide - Page 14

• Auto-detection of failed drives with transparent rebuild. There must be disk activity (I/O to the drive) for a missing drive to be marked as failed. • Auto-resume of initialization or rebuild on reboot (the Auto Rebuild feature must be enabled before virtual disk creation). • Smart initialization automatically checks consistency of virtual disks if there are five or more disks in a RAID 5 array, which optimizes performance by enabling readmodify-write mode. RAID 5 arrays of only three or four drives use Peer Read mode. • Smart Technology predicts failures of drives and electronic components. • Patrol Read checks drives and maps bad sectors. • Commands are retried at least four times. • Firmware provides best effort to recognize an error and recover if possible. • Failures are logged from controller and drive firmware, and SMART monitor. • Failures are logged in NVRAM, viewable from OS Event Log, Intel® RAID Web Console 2, CIM, and LEDs. • Multiple cache options allow configuration-specific performance optimization: - Write-back: Faster because it does not wait for the disk but data will be lost if power is lost. - Write-through: Usually slower but ensures data is on the disk. - Read Ahead: Predicts next read will be sequential and buffers this data into the cache. - Non Read Ahead: Always reads from the drive after determining exact location of each read. - Adaptive Read Ahead: Reads ahead and caches data only if doing sequential reads. - I/O setting. Determines whether read operations check the cache before reading from disks. ✧ Cache I/O: Checks cache first, only reads disk if data is not in the cache. ✧ Direct I/O: Reads data directly from disk. (not cache) • Redundancy through: - Configuration stored in non-volatile RAM and on the drives (COD). - Hot-swap support. - Optional battery backup for cache memory. SAS/SATA Features • Provides four independent PHYs, each supporting 3.0 Gbps SAS and SATA data transfers. • Scalable interface that supports up to 16 physical devices and 64 logical devices via expanders. 4 Intel® Integrated RAID Module SROMBSASMR Hardware User's Guide