Most server sizing mistakes happen at the spec stage — undersized RAM, overspecified CPU, wrong drive form factor, missed network throughput requirement. This walkthrough gives you the actual decision framework Servnet engineers use when specifying Dell PowerEdge, HPE ProLiant or Lenovo ThinkSystem for UK customers.
Step 1 — Workload profile first, hardware second
Document the workload before opening a configurator. CPU pattern (sustained vs bursty), memory footprint (working set + headroom), storage IOPS + throughput, network throughput, peak vs average. Most teams skip this and end up over- or under-spec'd.
For VM consolidation: count VMs at peak + sum vCPU + sum vRAM + sum storage IOPS + sum network. Add 30-50% headroom for failover + growth.
For databases: capture peak transactions/sec, working set size, log throughput, backup window.
Step 2 — CPU choice (Intel Xeon 6 vs AMD EPYC 9005)
Intel Xeon 6 — per-core performance leader, best for licensing-sensitive workloads (Oracle, SQL Server per-core), AI inference (AMX accelerator).
AMD EPYC 9005 (Turin) — core count + memory bandwidth leader, best £/vCPU at typical virtualisation densities, larger L3 cache helps memory-bound workloads.
Rule of thumb: VMware vSAN / Hyper-V / typical mid-tier virtualisation → AMD EPYC. Database / SAP HANA → benchmark both.
Step 3 — Memory sizing
DDR5-6400 is current (2026). 16 / 32 / 64 / 128 GB RDIMM are the practical step sizes.
16-24 GB per VM for typical virtualisation; 64+ GB per VM for VDI gold images; 128-512 GB+ for SAP HANA / large databases.
Size to 60-70% utilisation. 90%+ memory utilisation = no headroom for vMotion / failover / growth.
Mixed DIMM sizes hurt performance — populate balanced channels.
Step 4 — Storage choice
NVMe (U.2 / U.3 / E1.S / E3.S) is the default for new servers in 2026. SAS only where SSD chassis density demands it or legacy expansion shelves are in play.
SATA SSD only for cold-tier capacity workloads where IOPS doesn't matter.
PCIe Gen5 NVMe (E3.S form factor) is the current performance ceiling — 14+ GB/s sustained per drive.
For VM workloads: typically 2-6× large NVMe drives in RAID 1/10 or HBA-passthrough to software-defined storage (vSAN, Azure Stack HCI, Nutanix AOS).
Step 5 — Network
10 GbE = legacy default. 25 GbE = current standard for new builds. 100 GbE = high-throughput workloads (vMotion, storage replication, AI fabric).
For hyperconverged: 25 GbE minimum, 100 GbE for production at scale.
Mellanox ConnectX-7 / 8 or Intel E810 are current dual-port 25/100 GbE workhorses.
Step 6 — Form factor + PSU + management
1U for compute-dense / minimal storage; 2U for compute + balanced storage (the workhorse); 4U for GPU / max-storage.
Always specify dual redundant PSU sized for peak draw + 20% headroom.
Always specify the management licence (iDRAC9 Enterprise for Dell, iLO 7 Advanced for HPE, XClarity Controller Enterprise for Lenovo). Without it, you can't do KVM-over-IP / firmware updates remotely.
Step 7 — Support tier
24×7×4hr on-site = standard for production. NBD = acceptable for non-production. Servnet TPM matches or beats OEM SLA at typically 30-60% lower cost — see our TPM vs OEM TCO analysis.