Starting points by workload
These are typical starting points for a small or mid-sized business. Your software vendor's requirements always come first, and it is worth leaving room to grow.
| Workload | Typical starting point | What drives the need |
|---|---|---|
| File and print server | 16 to 32 GB | Number of users; extra memory is used as file cache |
| Domain controller | 8 to 16 GB | Size of the directory |
| Tally or a small ERP server | 16 to 32 GB | Number of users and company data size |
| Database server (SQL Server, MySQL, PostgreSQL) | 32 to 128 GB | Size of the active data: more of it in memory means fewer disk reads |
| Virtualization host | 64 to 256 GB or more | The total of all virtual machines (see below) |
| Backup or storage server | 16 to 64 GB | Backup software and file system; some, such as ZFS, use more |
Sizing a virtualization host
For VMware ESXi, Proxmox or Hyper-V, add up the memory you will give each virtual machine, then add some for the hypervisor and headroom for growth:
- List each virtual machine and the memory it needs, for example a domain controller (8 GB), a file server (16 GB), Tally (16 GB) and a database (32 GB): 72 GB.
- Add the hypervisor's own needs: a few gigabytes, more with software-defined storage.
- Add 25 to 50% headroom for growth and new virtual machines: in this example, about 96 to 128 GB.
A dual-socket 2U server such as the Dell R730 or R740 or the HPE DL380 has 24 memory slots, so you can start with what you need today and add modules later.
Choosing server memory
- ECC registered memory (RDIMM). Servers use error-correcting memory that detects and fixes small memory errors. Desktop memory will not work.
- RDIMM vs LRDIMM. Load-reduced modules (LRDIMMs) allow very large capacities. Do not mix RDIMMs and LRDIMMs in the same server.
- Match the generation. Xeon E5 v3/v4 servers (Dell R630/R730, HPE Gen9) use DDR4 up to 2400 MT/s. Xeon Scalable servers (Dell R640/R740, HPE Gen10) support faster DDR4. Check the server's supported memory list.
- Same size and speed. Use identical modules where possible. Mixed speeds all run at the speed of the slowest module.
Fitting memory correctly
How modules are placed matters as much as how much you buy. Memory is fastest when every channel is used evenly:
- Xeon E5 v3/v4 has 4 memory channels per CPU, so fit modules in sets of 4 per CPU (for example 8 modules in a two-CPU server).
- Xeon Scalable has 6 channels per CPU, so fit modules in sets of 6 per CPU (for example 12 modules in a two-CPU server).
- Two CPUs? Give both the same amount of memory. Each CPU can only reach its own slots directly.
- Fill the first slot of each channel first, following the slot order printed on the server's lid or in its manual.
An uneven layout, such as 5 modules on one CPU, still works but can noticeably reduce memory speed.
Need memory for a server you already have? See our server parts page, or read the Dell R730 vs R740 guide if you are choosing a new server.
Common questions
Can I add more RAM to my server later?
Yes, as long as there are free slots and the new modules match the type, speed and rank of the existing ones. Adding in balanced sets keeps memory at full speed.
Can I use desktop RAM in a server?
No. Servers such as the Dell PowerEdge and HPE ProLiant need ECC registered memory; desktop memory will not be recognised.
Does more RAM make a server faster?
Only up to the point where the workload fits in memory. Beyond that, faster storage, more CPU cores or better memory layout make more difference.
How much RAM does a Tally server need?
For a small team, 16 to 32 GB is a common starting point. Add more for more users or a large company data set, and leave room to grow.