What makes a server a storage server

Any server can hold data. A storage server is one where the drives, the controller and the network set the specification, and the processor is chosen to keep up with them. In practice that means a chassis with plenty of hot-plug bays, a controller that suits how you want to manage the disks, enough memory for caching, and network ports fast enough that clients are not left waiting.

The same box can play several roles. It might be a file server for a department, a backup target for your hypervisor hosts, an object store behind an application, or one node in a private cloud. The role decides which of those four parts gets the money.

Cloud storage servers on your own hardware

People searching for cloud storage servers usually mean one of two things. Either they want to rent capacity from a provider, or they want something that behaves like cloud storage but sits in their own rack. This guide is about the second.

A private cloud storage setup is mostly software. S3-compatible object stores, file sync platforms such as Nextcloud and distributed systems such as Ceph all run on standard x86 servers. What they ask of the hardware is predictable: lots of disks the operating system can see directly, reliable networking between nodes, and enough RAM and CPU to handle checksums, replication or erasure coding without becoming the bottleneck.

For a single site, one well-specified server is often enough to start. Distributed systems are different. They are designed to spread data across several machines, so three modest nodes usually make more sense than one large one. Check the minimum node count in the documentation for the software you plan to run before you choose hardware.

Rack or tower server storage

Most storage servers are rack-mount, because a 2U chassis packs a lot of bays into a small space and slots into existing power and cooling. But tower server storage still has a place. In an office without a rack or a cooled room, a tower with a handful of large drives makes a quiet, sensible file and backup server.

Dell tower server storage in the PowerEdge T-series is a good example: the towers are managed with the same tools as the rack models, so the skills carry over if you move into a rack later. If you are torn between the two, our guide to choosing between rack and tower servers covers noise, space and expansion in more detail.

Drive bays and disk choice

Bays come in two sizes. 3.5in large form factor (LFF) bays hold the biggest hard drives and give the lowest cost per terabyte. 2.5in small form factor (SFF) bays hold more drives in the same space and suit SSDs. Server HDD storage is still the right answer for bulk data, backups and archives. SSDs earn their place for virtual machine storage, databases and as a cache in front of hard drives.

Do the capacity sums before you pick a chassis. Say you need about 40TB usable. RAID 6 across eight drives gives up two drives' worth of space to parity, so eight 8TB drives give roughly 48TB before formatting. That fits, but it leaves little headroom if the chassis has only eight bays. A chassis with spare bays lets you add a second set later instead of replacing everything.

A SAS storage server has a SAS controller and backplane. These will normally run SATA drives too, which is handy for cheaper bulk disks, but a SATA-only controller will not run SAS drives. SAS drives add dual-port connections and better error handling, which matter more as drive counts grow. Our SAS, SATA and NVMe comparison explains where each interface fits, and the guide to enterprise and consumer SSDs covers why endurance ratings matter in a server that writes all day.

Storage controllers: RAID or HBA

The controller decides who manages the disks. A hardware RAID controller builds the arrays itself and presents finished volumes to the operating system. Models with a protected write cache can speed up writes noticeably, and they keep things simple on Windows Server or VMware hosts.

An HBA, or a RAID controller running in HBA mode, passes each disk straight through. That is what ZFS, Ceph and Storage Spaces Direct want, because they do their own redundancy and need to see every drive's health directly. Putting ZFS on top of a hardware RAID volume works, but it hides the information ZFS relies on to detect and repair errors.

On Dell systems the controllers are the PERC family; HPE uses Smart Array. When people look for server Dell storage controllers or Dell compatible data storage controllers, the main point is matching the controller to the server generation, the backplane and its cables. Some controllers switch between RAID and HBA modes and some do not, so check the exact model. Third-party cards can work, but the server may not monitor them or manage fans in the same way, so it depends on the card and chassis. Our guide to how RAID controllers work goes deeper on cache, RAID levels and modes.

Memory, processor and network

Storage servers rarely need the fastest CPUs. A modest core count is fine for file serving. Compression, encryption, erasure coding and deduplication all add load, so give a distributed or ZFS-based build more cores than a plain file share.

Memory matters more than people expect. ZFS uses spare RAM as a read cache, so more memory often means faster reads with no other change. Deduplication needs much more again, and is best avoided unless you have tested it. Registered memory is standard in these servers, and our guide to RDIMM and LRDIMM server memory explains which type suits high capacities.

The network is the most common bottleneck. A single 1GbE link moves roughly as much data per second as one large hard drive reading sequentially, so an array of eight disks behind it spends most of its time waiting. For anything beyond a small office, plan for 10GbE or faster, and give storage traffic its own links in a cluster. Our enterprise networking guide covers the switches and adapters involved.

Dell, HPE, Supermicro and others

The HPE ProLiant DL380 is the general-purpose 2U server many teams already know, and a DL380 storage server is simply one built with a drive cage, controller and network cards chosen for capacity. Dell takes a similar approach, with xd models such as the PowerEdge R740xd offered as storage-focused versions of the standard chassis. Newer platforms like the Dell PowerEdge R750 suit storage roles that also need serious compute.

Supermicro storage servers take a more modular route, with a wide range of chassis and boards built from fairly standard parts. A Supermicro storage server is a common choice for ZFS and Ceph builds where you want control over every component and no ties to one vendor's tools.

If you are weighing up Huawei data storage or another dedicated array against a server-based design, the trade-off is familiar. A dedicated array bundles controllers and software into one managed product. A server-based design costs less to expand and lets you choose the software, but you take on more of the setup and support yourself. Whichever brand you consider, check how easily you can get firmware, spares and support in the UK.

Storage servers for backup

A refurbished data storage and backup server is one of the easiest places to save money, because backup storage values capacity over speed. Large LFF hard drives in RAID 6 or a ZFS pool give plenty of space at a low cost per terabyte.

Keep the backup server separate from the systems it protects. If the backups sit on the same host as production, one failure or one ransomware infection can take out both. Follow the 3-2-1 approach: three copies of the data, on two different types of media, with one copy off site. Many teams run backup targets on Linux, and a server with Debian pre-installed gives you a clean base to install your backup software on.

Buying refurbished storage servers

Storage is a good fit for refurbished hardware. The chassis, backplanes and controllers in recent generations are mature and well documented, and the money you save on the server can go into drives, which is where storage budgets are really spent. Refurbished storage servers also leave room in the budget for a second node or a separate backup box.

Buying the server and drives together avoids the usual problems with caddies, firmware and controller compatibility. Refurbished Dell server and storage bundles, or any configured build, arrive with drives fitted and arrays set up the way you asked. You can spec one in the server configurator, or browse refurbished rack servers for a chassis to build on. Configured servers come with a three-year return-to-base warranty, and the warranty information page has the full terms.

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