Not every RAID volume on a PowerEdge or ProLiant server comes from a full RAID controller. Entry servers can use software RAID built into the platform, and many servers boot from a small mirrored M.2 device while the main drives hold data. This guide compares the three options as Dell and HPE document them: hardware RAID controllers, platform software RAID (Dell PERC S160, HPE Smart Array S100i) and boot-optimized devices (Dell BOSS-S2 and BOSS-N1, HPE NS204i).
Before you start
- Check the operating system support list of the RAID option you plan to use. Software RAID support differs sharply between Windows, Linux and VMware.
- Software RAID needs the vendor driver during OS installation on Windows.
- Creating a RAID volume on drives that already hold data destroys that data. Back up first.
Hardware RAID controllers
A hardware controller such as a Dell PERC H965 or an HPE Smart Array P-class or MR 400 series card has its own RAID-on-chip processor and cache memory. Dell's PERC 12 specification table, for example, lists a Broadcom RAID-on-chip, 8 GB of DDR4 cache and an Energy Pack for the H965i adapter. The controller presents finished virtual disks to the OS, so RAID works the same under Windows, Linux and VMware ESXi, and write-back cache can be protected against power loss (see controller cache).
Most current controllers can also pass drives straight to the OS: Dell lists non-RAID support on PERC 12, and HPE SR and MR controllers run in mixed mode, where drives not in a logical drive are presented to the OS. That is how you give whole drives to OS-level software RAID such as ZFS (see Proxmox storage with LVM and ZFS).
Dell PERC S160 software RAID
- A software RAID solution for PowerEdge systems that supports up to 30 NVMe SSDs, SATA SSDs and SATA HDDs, depending on the backplane. SAS drives are not supported, and Dell lists a minimum of 16 GB system RAM.
- Windows: Volume, RAID 0, 1, 5 and 10 on SATA and NVMe drives. Supported versions listed: Windows Server 2019, 2022 and 2025.
- Linux: the S160 UEFI utility creates a RAID 1 boot virtual disk from two identical drives; after the OS boots, the Linux native RAID driver (MDRAID) manages it. Non-boot volumes are created with native Linux RAID tools. The guide lists Red Hat Enterprise Linux and SUSE Linux Enterprise Server versions.
- Cache: the S160 uses part of system memory as cache. The default is No Read Ahead, Write Through; Dell recommends a UPS before enabling Write Back. Cache policies cannot be set on NVMe SSDs.
- Servers: the guide lists 16G models such as the R660, R760, R6625 and R7625; check the guide for the full list.
VMware ESXi does not appear in the S160 supported operating system list, so plan ESXi on a hardware controller or a BOSS device.
HPE Smart Array S100i SR Gen10 software RAID
- Supported only on Windows (Windows Server 2016, 2019 and 2022 are listed). For Linux and VMware, HPE refers you to the S100i QuickSpecs.
- SATA drives only, up to 14 SATA lanes, RAID 0, 1, 5 and 10, UEFI boot mode only, and system memory used as read cache.
Step 1 — Enable Smart Array SW RAID (Gen10)
- Reboot the server and press F9 during POST to open System Utilities.
- Select System Configuration > BIOS/Platform Configuration (RBSU) > Storage Options > SATA Controller Options > Embedded SATA Configuration.
- Choose Smart Array SW RAID Support and click OK. If a warning says Smart Array SW RAID is not supported when the boot mode is Legacy BIOS, click OK; HPE lists UEFI boot mode as a prerequisite.
- Press F12 to save and exit, confirm Yes-Save Changes, then click Reboot.
During Windows setup you may need to load the S100i driver manually. For Gen11 servers, check the server's QuickSpecs for the embedded software RAID option and its OS support.
Dell BOSS boot devices
BOSS-S2 is a RAID card designed for booting the operating system, with two 80 mm M.2 SATA SSDs. Its specification table lists RAID 1 and non-RAID (no RAID 0), one virtual disk, write-through only with no controller cache or battery, a fixed 64K stripe, hot-plug of the M.2 drives, automatic rebuild only, and no hot spare, patrol read or consistency check. Dell recommends using BOSS-S2 only as an OS boot device. It is managed from the UEFI RAID utility (F2), OpenManage Storage Management, the BOSS-S2 CLI, iDRAC and Lifecycle Controller.
BOSS-N1 uses M.2 NVMe SSDs and supports single-drive RAID 0 and dual-drive RAID 1, with no non-RAID mode, no controller cache and no battery. Physical disk hot-plug is listed for the BOSS-N1 Monolithic but not for the Modular ET and Modular versions. Dell notes that the iDRAC interface cannot import a foreign virtual disk on BOSS-N1; use HII or delete the virtual disk.
HPE NS204i boot devices
- HPE describes boot devices as controllers supporting RAID 1 that auto-create a RAID 1 volume during boot, so they need no configuration, and mirror the deployed OS through dedicated hardware RAID 1.
- The NS204i-u holds two hot-pluggable 2280 M.2 NVMe SSDs; the NS204i-p is a PCIe card with two 22110 or two 2280 M.2 NVMe SSDs. Platform-specific versions exist; see the server QuickSpecs.
- Compatible OS: Windows, Linux and VMware, using the OS's native inbox NVMe drivers.
- You install the OS on the boot device; after installation completes, the system automatically copies it to the second mirrored drive. Rebuilds after a drive replacement are automatic and visible in the drive LED, UEFI, the iLO storage tab or Redfish.
Warning: Before replacing an NS204i drive, HPE says to back up all server data, check the drive bay LEDs or the IML to find the failed drive, and use a replacement SSD of the same capacity.
Comparison
| Option | Drives | RAID levels | Cache | OS notes |
|---|---|---|---|---|
| Hardware RAID (PERC H-series, HPE SR/MR) | SAS, SATA, NVMe by model | Up to 0, 1, 5, 6, 10, 50, 60 | Dedicated, battery or energy pack on cached models | OS independent |
| Dell PERC S160 | SATA, NVMe | Windows: Volume, 0, 1, 5, 10. Linux: RAID 1 boot + MDRAID | System memory | Windows Server, RHEL, SLES |
| HPE S100i SR Gen10 | SATA | 0, 1, 5, 10 | System memory (read) | Windows only |
| Dell BOSS-S2 | 2 × M.2 SATA | RAID 1, non-RAID | None (write-through) | See Dell OS support list |
| Dell BOSS-N1 | 2 × M.2 NVMe | RAID 0 (1 drive), RAID 1 | None (write-through) | See Dell OS support list |
| HPE NS204i | 2 × M.2 NVMe | RAID 1 (automatic) | None listed | Windows, Linux, VMware |
Frequently asked questions
Which option suits a VMware ESXi host?
Boot ESXi from a boot device or a hardware RAID volume, and keep VMs on a hardware RAID array. HPE lists VMware as compatible with NS204i; the S160 and S100i guides do not list ESXi. Install guides: ESXi on PowerEdge and ESXi on ProLiant.
Can a BOSS card hold data volumes too?
Dell recommends using the BOSS-S2 card only as an operating system boot device, and it supports a single virtual disk.
Checklist
- Hypervisor or OS boot: mirrored boot device (BOSS-S2, BOSS-N1 RAID 1, NS204i) or a RAID 1 on the main controller.
- Busy data volumes: hardware RAID with protected cache.
- Entry Windows server without a RAID card: PERC S160 (16G) or S100i (Gen10), with the driver ready for setup.
- Linux on S160: RAID 1 boot from the S160 utility, then MDRAID.
- OS-level RAID or ZFS: present drives as non-RAID, HBA or JBOD.
- OS support list checked before ordering.
Skyline can supply, configure and maintain Dell, HPE and Huawei servers under an annual maintenance contract (AMC). Contact us.
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