HP
HP 631667-B21 Smart Array P222 SAS Controller
★★★★★
Adds enterprise-grade RAID protection and 512MB flash-backed write cache to ProLiant Gen8 servers, turning unprotected direct-attach storage into a fault-tolerant array.
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Overview
Enhance Your Storage Performance with Advanced RAID Control
The HP Smart Array P222 Controller is a high-performance RAID controller designed to optimize storage performance and data protection for HP ProLiant Gen8 servers. With support for SAS and SATA drives, it offers advanced features such as online RAID migration and flash-backed write cache.
Specifications:
- Brand: HP
- Model: 631667-B21
- Interface: PCIe 3.0
- SAS Ports: 1 Internal, 1 External
- Data Transfer Rate: 6 Gb/s
- Cache Memory: 512MB FBWC (Flash Back Write Cache)
- Form Factor: Low Profile
- Compatibility: HP ProLiant Gen8 Rack and Tower Servers
Key Features
It features four internal and four external SAS ports and delivers increased server uptime by providing advanced storage functionality, including online RAID level migration with flash back write cache, global online spare, and pre-failure warning.
Data compatibility between HP Smart Array Controllers means customers can easily upgrade to future Smart Array Controllers.
HP Smart Array Advanced Pack 2.0 firmware makes it easier for customers to protect their data with advanced functionality for this next generation of Smart Array controllers, including features such as RAID 1 ADM
Pros & Cons
👍 Pros
- 512MB Flash-Backed Write Cache enables write-back caching with power-loss protection — directly reducing write latency under sustained sequential and random I/O workloads compared to write-through configurations.
- Online RAID level migration allows array reconfiguration without server downtime, a measurable operational advantage in 24/7 production environments.
- PCIe 3.0 interface ensures the host bus is not the bottleneck for multi-port aggregate throughput at 6 Gb/s SAS-2 speeds.
- RAID 1 ADM support via Advanced Pack 2.0 firmware provides triple-mirror protection beyond standard RAID 1, adding resilience against simultaneous dual-drive failures.
- Data compatibility with future HP Smart Array controllers means arrays can be migrated to a replacement or upgraded controller without reformatting — protecting the investment in existing storage configurations.
👎 Cons
- Validated exclusively for ProLiant Gen8 servers — not compatible with Gen9 or later platforms, limiting its value in environments planning a server hardware refresh.
- 6 Gb/s SAS-2 throughput per port is a full generation behind SAS-3's 12 Gb/s — a tangible ceiling for NVMe-class or high-density SSD workloads, though not a limitation for spinning disk arrays.
- Low-profile form factor restricts installation to chassis with low-profile PCIe slots; standard full-height bracket adapters are required for tower servers with standard slots.
- HP Smart Array Advanced Pack 2.0 firmware features (including RAID 1 ADM) may require a separate license purchase — power users should confirm whether advanced RAID features are included or sold separately.
Frequently Asked Questions
Which servers is the HP P222 compatible with?
The P222 is validated for HP ProLiant Gen8 rack and tower servers. It is not forward-compatible with Gen9 or later platforms without verification, as HP Smart Array controllers are generation-specific in firmware and driver stack. If you are deploying into a mixed-generation environment, confirm the server model before ordering.
What RAID levels does the P222 support?
The P222 supports standard RAID levels including RAID 0, 1, 5, 6, and 10, as well as RAID 1 ADM (Advanced Data Mirroring) through HP Smart Array Advanced Pack 2.0 firmware. RAID 1 ADM adds a third mirrored drive to a RAID 1 pair, providing an additional layer of protection against simultaneous dual-drive failures without the overhead of RAID 6.
What does the 512MB Flash-Backed Write Cache actually do for I/O performance?
The FBWC allows the controller to acknowledge write operations to cache rather than waiting for the physical drive to confirm the write — a technique called write-back caching. This dramatically reduces write latency under sustained I/O workloads. The flash backing ensures that cache contents survive a power loss event, so data is not lost before it flushes to disk, which is the critical safety difference between battery-backed and unbuffered write caching.
Can I migrate between RAID levels without taking the array offline?
Yes. The P222 supports online RAID level migration, meaning you can move from RAID 5 to RAID 6 (for example) while the server remains in production. This is a significant operational advantage for environments where downtime windows are constrained.
What is the data transfer rate, and does PCIe 3.0 matter for this controller?
The P222 operates at 6 Gb/s per SAS port, which is the SAS-2 specification. The PCIe 3.0 host interface provides sufficient bandwidth headroom so that the PCIe slot itself is not the bottleneck — at 6 Gb/s per port, the aggregate throughput across multiple active ports still fits comfortably within PCIe 3.0 x8 bandwidth.
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