Comparison Synology DiskStation DS1525+ vs Synology DiskStation DS925+

The number of slots for drives in the form factor 3.5", provided in the design of the server.

Initially, 3.5 "is the traditional, most popular form factor of drives for server systems. It is noticeably larger than 2.5", but it allows you to create capacious, inexpensive (in terms of gigabytes) and reliable media, in which it is also easier to implement various additional functions. That is why, specifically in NAS servers, this form factor is also the most popular; slots under 2.5" are much less common in such equipment, and in most cases they complement 3.5".

As for the number of slots, it can vary from 2 (or even 1) in the most basic desktop systems to 8 or more in professional rack-mount solutions. And not only their maximum capacity depends on the specific number of drives, but also some other features of work — first of all, the physical possibility of using one or another RAID level.

The number of PCIe slots available in the NAS server design.

PCIe is one of the most popular modern interfaces for connecting internal components to a computer's motherboard. Specifically in NAS servers, it can be used for wireless adapters and SSDs; in the latter case, PCIe allows for higher speeds than SATA and fully realizes the potential of solid-state memory. The number of such slots corresponds to the number of PCIe components that can be installed in the server simultaneously.

Note that PCIe connections can use different numbers of lanes (1x, 4x, 16x), and for normal operation, the slot on the "motherboard" should have no fewer lanes than the component being installed. In practice, this means that a component with a 1x slot can fit into any slot without issues, but for larger slots, the connection capability should be clarified separately. However, in the case of NAS servers, even the capabilities of PCIe 4x are rarely required, let alone 16x.

A modern universal connector for connecting external drives, flash drives, docking stations, or other compatible devices. It may not be limited to a single USB-C port and also provides for different versions that affect data transfer speed.

The amount of RAM on the NAS server. Along with the processor, it is one of the indicators that determine the speed of the system — the more memory, the higher the computing power. However, in fact, it does not always make sense to chase large amounts of "RAM", which can reach 4 GB, 8 GB and even higher; see "Processor" for details.

The amount of power consumed by the NAS server during normal operation. Most often, we are talking about maximum power consumption — with all the occupied slots for drives, under high load.

Modern NAS, even high-performance ones, have rather modest power consumption — even among professional models with 10 or more drives, this figure rarely exceeds 1 kW. So there are no problems with connecting to a 230 V network. However, energy consumption information can be useful for some special applications, primarily for estimating the load on UPSs, emergency generators, stabilizers, and other special equipment.

The noise level produced by the device during operation. These data will be useful, first of all, to those who are trying to reduce the noise level as much as possible and, as they say, “fight for every decibel”. However, it is worth noting here that manufacturers can cheat and indicate the noise level for different modes.