If you've configured or shopped for an HPE ProLiant Gen10 or Gen10 Plus server, you've almost certainly run into a wall of alphanumeric controller names — P408i-a, E208i-p, P816i-a, MR416i-a, and so on. They all look similar, but the differences between them affect RAID support, performance, cache, and even which drive types you can connect.
This guide breaks down HPE's Smart Array naming convention, walks through each controller tier, and helps you match the right controller to your workload — whether you're speccing a new build or trying to figure out exactly what's already inside a refurbished HPE ProLiant server you're considering.
Decoding the Naming Convention
HPE's Gen10-era Smart Array controllers follow a consistent naming pattern once you know what each part means.
Letter Prefix — Controller Tier
Software RAID
OS-driven RAID, no dedicated hardware cache.
Essential
Hardware RAID (0,1,5,10) for SAS/SATA, no FBWC.
Performance / Premium
Full RAID levels including 6, 50, 60 with Flash-Backed Write Cache.
Trimodal (Gen10 Plus)
NVMe + SAS + SATA through a single PCIe 4.0 controller.
Numeric Lane Count
The number in the name (e.g., 04, 08, 16) identifies how many SAS/SATA lanes the controller provides — most commonly 4, 8, or 16 internal lanes, roughly mapping to how many drives it can address directly (with expanders, a controller can address more drives than its lane count).
Internal / External Designator
- "i" — internal ports only
- "e" — external ports only
- "ie" (e.g., P416ie-m) — both internal and external ports
Form Factor Suffix
Put it together: P408i-a = Premium tier, 8 internal SAS/SATA lanes, AROC form factor (dedicated slot, no PCIe lane used).
S-Class: Software RAID (S100i)
The S100i SR is the entry-level option, typically found as a low-cost embedded controller on Gen10 servers. It supports SATA drives only (no SAS), provides basic RAID 0/1/5/10, and relies on the host OS for RAID processing rather than dedicated hardware.
- SATA drives only — no SAS support
- RAID 0, 1, 5, 10 (OS-driven, not hardware)
- No Flash-Backed Write Cache
- Supported in UEFI mode only
- Suitable for boot drives or lightweight configurations
E-Class: Essential (E208i-a, E208i-p, E208i-c)
The E-series sits a step up, offering true hardware RAID for the most commonly used levels — 0, 1, 5, and 10 — across both SAS and SATA drives. These controllers operate in Mixed Mode, meaning they can run RAID and HBA (pass-through) operations simultaneously, and they support data-at-rest encryption.
What they lack compared to the P-series is Flash-Backed Write Cache. This makes them a solid, cost-effective choice for general-purpose servers where RAID 5/10 covers your redundancy needs and you're not chasing maximum write-intensive performance.
- SAS 12Gb/s and SATA support
- RAID 0, 1, 5, 10
- Mixed Mode: RAID + HBA simultaneously
- Data-at-rest encryption supported
- No Flash-Backed Write Cache
P-Class: Performance (P408i-a, P408i-p, P816i-a, P204i)
The P-series is HPE's full-featured hardware RAID line. In addition to RAID 0, 1, 5, and 10, it adds RAID 6, 50, and 60 for environments that need extra parity protection or larger arrays. The defining feature is Flash-Backed Write Cache — typically 2GB on Gen10 P-series controllers — which dramatically reduces write latency for database and logging-heavy workloads.
P408i-a (most common)
8 internal lanes, AROC form factor. The standard controller in DL380/DL360 Gen10 builds. Hits the sweet spot of RAID 6 support and cache-backed performance without consuming a PCIe slot.
P816i-a (high-density)
16 internal lanes, AROC. Doubles lane count for 24-bay SFF chassis builds. Avoids the need for expanders and keeps wiring simpler in high drive-count configurations.
- RAID 0, 1, 5, 6, 10, 50, 60
- 2GB Flash-Backed Write Cache (requires Smart Storage Battery)
- HPE SSD Smart Path for accelerated SSD reads
- Optional SmartCache for SSD/HDD caching scenarios
Gen10 Plus and the MR-Series: Trimodal NVMe/SAS/SATA
When HPE moved to Gen10 Plus, it introduced the MR-series (e.g., MR416i-a, MR416i-p) — "Trimodal" controllers that can address NVMe, SAS, and SATA drives through the same controller on PCIe 4.0.
Earlier Gen10 P-series controllers handle SAS/SATA RAID, but NVMe drives in those systems typically connect directly to the CPU's PCIe lanes rather than through the RAID controller. The MR-series consolidates that, simplifying backplane design and giving you RAID protection options across mixed drive types in a single card.
- NVMe + SAS + SATA through a single controller
- PCIe 4.0 interface for higher bandwidth
- Up to 8GB FBWC on higher-end models
- SmartCache included standard (not an add-on license)
- Available as AROC (-a) and PCIe (-p) variants
Gen10 Plus builds with NVMe in the mix should look at the MR416i-a/p Trimodal controllers — they're the only way to bring NVMe under the same RAID management framework as your SAS/SATA drives.
Quick Comparison Table
| Controller | Tier | Lanes | Form Factor | Interface | Cache | RAID Levels |
|---|---|---|---|---|---|---|
| S100i SR | Software (S) | Up to 14 SATA, no SAS | Embedded | SATA 6Gb/s | None | 0, 1, 5, 10 (SW) |
| E208i-a / E208i-p SR | Essential (E) | 8 int. SAS/SATA | AROC or PCIe | SAS 12Gb/s, PCIe 3.0 | None | 0, 1, 5, 10 |
| P408i-a / P408i-p SR | Premium (P) | 8 int. SAS/SATA | AROC or PCIe | SAS 12Gb/s, PCIe 3.0 | 2GB FBWC | 0, 1, 5, 6, 10, 50, 60 |
| P816i-a SR | Premium (P) | 16 int. SAS/SATA | AROC | SAS 12Gb/s, PCIe 3.0 | 2GB FBWC | 0, 1, 5, 6, 10, 50, 60 |
| MR416i-a / MR416i-p | Trimodal (MR) | 16 NVMe/SAS/SATA | AROC or PCIe | SAS 12Gb/s, PCIe 4.0 | Up to 8GB FBWC | 0, 1, 5, 6, 10, 50, 60 |
Choosing the Right Controller for Your Workload
A few questions narrow it down quickly when you're building or buying a server.
Do you need RAID 6, 50, or 60?
If your array needs to survive two simultaneous drive failures, or you're building large arrays where rebuild times matter, you need a P-series or MR-series controller. The E-series and S100i don't support these levels.
Are you running write-heavy workloads like databases or logging?
Flash-Backed Write Cache on the P-series (or MR-series) significantly reduces write latency. For E-series or S100i, writes go straight to disk — fine for read-heavy systems, but a bottleneck under sustained database writes.
How many drives are you connecting?
An 8-bay SFF chassis is comfortably served by an E208i or P408i (8 lanes). For a 24-bay SFF chassis or mid-tray/rear drive cages, the P816i-a with 16 lanes avoids expanders and keeps wiring simpler.
Are you mixing NVMe drives into the array?
On Gen10 systems, NVMe typically bypasses the Smart Array controller entirely. On Gen10 Plus, the MR-series Trimodal controllers bring NVMe into the same RAID management framework as your SAS/SATA drives.
Does the controller need a PCIe slot, or do you have a dedicated storage slot?
The -a (AROC) variants drop into a dedicated slot and free up PCIe slots for NICs, GPUs, or other cards — generally the preferred option when the chassis has the AROC slot available. The -p variants occupy a PCIe slot, useful when adding or replacing a controller in a chassis without a free AROC slot.
A Note on the Smart Storage Battery
Any Gen10 controller with Flash-Backed Write Cache (the P-series and MR-series) requires an HPE Smart Storage Battery to protect cached writes during a power loss. The battery is sold separately and can be shared across multiple controllers in the same chassis.
If you're buying a P408i-a or P816i-a separately from a complete server build, make sure a battery — or an existing shared battery with available capacity — is part of the configuration.
Final Thoughts
The naming scheme can look intimidating, but it boils down to three questions: what RAID levels do you need (S/E/P/MR), how many drives are you connecting (the lane count), and what slot does your chassis have available (-a, -p, -c, -b, -m).
General-purpose DL380/DL360
P408i-a — RAID 6, 2GB FBWC, AROC (no PCIe slot used)
High-density 24-bay chassis
P816i-a — 16 internal lanes, avoids expanders
Gen10 Plus with NVMe
MR416i-a/p — Trimodal NVMe/SAS/SATA, PCIe 4.0
Whatever your configuration needs, confirm the controller model, lane count, and form factor against your specific chassis before purchasing — and don't forget the Smart Storage Battery for any P-series or MR-series card.
