Choosing a server RAID controller
A RAID SAS controller sits between the server's PCIe bus and its drive backplane. It presents disks to the operating system either as RAID volumes or, in HBA mode, as individual drives. Picking the right one comes down to three checks: the server platform, the form factor the chassis expects, and whether your workload needs protected write cache. This range covers Dell PERC, HPE Smart Array, Fujitsu, Cisco and LSI/Broadcom hardware, with the batteries, cables and enablement cards that tend to get forgotten until the card is already in the chassis. For background on how hardware RAID handles parity and caching, our guide to understanding RAID controllers is a good primer.
At a glance
Matching the controller to your server
Dell PowerEdge RAID controllers
On 13th and 14th-generation PowerEdge (R630, R730, R640, R740 and their tower equivalents) the PERC usually lives in the Mini Mono slot, so a Mini Mono card and a PCIe adapter of the same model are not interchangeable. The PERC H330 is the entry controller, typically used for boot mirrors and pass-through. The PERC H730P, including the H730P Mini, adds battery-backed write cache for parity arrays and busier volumes. If a controller reports a failed or degraded battery, the H132V battery and bracket for H730 and H730P cards or the NWJ48 battery for the H740 and H740P brings write-back cache back without replacing the card.
HPE ProLiant RAID controllers
HPE splits Smart Array by generation and form factor. On Gen9 ProLiant, such as the DL360 Gen9 and DL380 Gen9, the HPE P440ar with 2GB cache is the usual AROC choice for RAID 5 and RAID 6. On Gen10, the E208i-a is the cacheless entry controller, suited to boot volumes and mixed-mode setups where some drives are passed straight to the operating system. Cached Smart Array controllers rely on the server's Smart Storage Battery for write-back mode, so check that it is fitted and healthy before blaming the HP RAID card for slow writes.
Typical deployments
Boot and OS mirrors
Two small drives in RAID 1 for the hypervisor or operating system need very little from the controller. A cacheless card is fine here. Prioritise the correct form factor for the chassis and a firmware level the server's management tools recognise. Cache size matters far less.
Virtualisation datastores
Local datastores on RAID 5, 6 or 10 live or die by write cache. Parity writes without protected cache are slow enough to make a host feel undersized when the CPUs are idle. Choose a cached controller with a working battery, and keep controller models consistent across hosts so spares and firmware stay simple.
SQL and database servers
Databases generate small random writes and depend on the transaction log. RAID 10 avoids the parity penalty. Put logs and data on separate volumes where the bay count allows, and treat a healthy cache battery as mandatory: losing write-back cache can quietly cut write throughput.
ZFS, Ceph and Storage Spaces Direct
Software-defined storage wants raw disks and direct access to drive health data, not a hardware RAID volume underneath. Run the controller in HBA or pass-through mode, or use a dedicated HBA. Never layer software RAID on top of hardware RAID; it hides failures from the layer that needs to see them.
NVMe performance tiers
NVMe drives bypass the SAS controller and connect over PCIe. On 14th-generation PowerEdge that means an enablement card such as the Dell CDC7W U.2 NVMe enablement card plus the correct backplane cabling. Confirm which bays your backplane wires for NVMe before you order drives.
SAN-attached hosts
If the data lives on a shared array, the local controller only handles boot. Spend on the fabric instead: a Fibre Channel HBA such as the Dell QLE2690 16Gb single-port card connects the host to the SAN, and a cacheless controller mirrors the boot drives.
Why buy from Compuwyze
- Controllers from Dell, HPE, Fujitsu, Cisco and LSI alongside the matching batteries, cables and enablement cards, so a full storage repair can go in one order.
- Orders for simple items placed before 2pm aim to ship the same day.
- Free UK delivery on orders over £50, normally next working day once shipped.
- International shipping via FedEx economy and priority services, usually 2 to 5 days.
- A 12-month return-to-base warranty on controllers and components.
- Returns accepted within 30 days, with return shipping paid by the customer.
Frequently asked questions
What does a RAID SAS controller actually do?
It connects the server's drives to the PCIe bus and, in RAID mode, combines them into logical volumes. It handles parity calculation, rebuilds and caching on its own processor instead of the host CPU. A plain SAS controller or HBA does the connection part only and passes each disk to the operating system individually. Most modern PERC and Smart Array cards can do either, depending on how they are configured.
Is a hardware RAID controller necessary?
Not always. Windows Server, VMware and Linux hosts with local parity arrays benefit from a cached hardware controller, and hypervisors such as ESXi do not offer their own software RAID for local disks. ZFS, Ceph and Storage Spaces Direct want an HBA instead. For a simple boot mirror, an entry controller is enough.
Can I replace a RAID controller without losing data?
Usually, yes. The array configuration is stored on the drives as well as the controller. A replacement from the same family, such as one PERC H730P for another, will normally detect it as a foreign configuration that you can import. Moving between controller families is less predictable. Take a verified backup first, keep the drives in their original bays, and do not initialise anything the new card offers to create.
Which RAID level should I use: RAID 0, RAID 1 or RAID 5?
RAID 0 stripes data for speed with no redundancy, so one failed drive loses the whole volume. Keep it for scratch space. RAID 1 mirrors two drives and is the standard choice for boot volumes. RAID 5 gives you the capacity of all but one drive and survives a single failure, but writes are slower without cache, and rebuilds on large drives take long enough that many admins prefer RAID 6 or RAID 10.
Do I need a battery for the controller cache?
For write-back cache, yes. The battery protects data held in cache if power is lost, and most controllers drop to write-through mode when the battery is missing or failing, which slows writes noticeably. Older RAID batteries are a common failure point, so it is worth replacing one before replacing the whole card. Accessories such as the LSI 13.5V RAID battery are in the components range.
Will a Dell or HPE RAID card work in a different vendor's server?
Stick to the vendor's own controller where you can. PERC, Smart Array and Cisco cards are built and tuned for their own platforms. In a different vendor's chassis, the management controller may not monitor them, and modular formats such as Mini Mono and AROC will not physically fit. A SATA RAID controller cannot run SAS drives, whereas a SAS controller runs both.