405139-B21 is an HP 256MB Battery-Backed Write Cache (BBWC) module designed for the Smart Array P400 and P400i RAID controllers. It provides cache memory for improving RAID write performance and helps protect cached data during a power interruption when used with the appropriate battery-backup configuration. HP QuickSpecs specifically identify this part as the HP Smart Array P400 256MB FIO Cache Module and state that it supports the P400 and P400i controllers.
- Part Number: 405139-B21
- Manufacturer: HP / HPE
- Product: Smart Array P-Series 256MB BBWC Cache Module
- Cache Capacity: 256MB
- Cache Type: Battery-Backed Write Cache (BBWC)
- Controller Compatibility: HP Smart Array P400 / P400i
- Application: RAID controller write caching and data protection
- Interface: Dedicated Smart Array cache-module interface
- Compatible Systems: HP ProLiant systems equipped with supported P400/P400i controllers, including DL360 G5, DL380 G5, DL365 G5, DL785 G5 and BL680c G5 configurations.
- Included: 1 × 256MB cache module
- Related Battery: 398648-001 — P-Series 4.8V BBWC battery
- Related Option: 405148-B21 — 512MB battery-backed cache upgrade
- Related Controller: 405132-B21 — Smart Array P400/256MB controller
- Compatibility Note: 405139-B21 is a cache module, not a complete RAID controller. HP documentation specifies compatibility with Smart Array P400 and P400i controllers.
