And finally, the servers have a PCIe slot for an add-on card. In this case, you can use it to add 10Gbps connectivity to the servers -- another must if you're into Multi-Gig.

The DS1621+is pretty efficient (we peaked at 77 watts with drives, but mostly used under 40 watts) so the fans did not have to work too hard, but a decent drive amount of noise escapes the NAS. PCIe add-in cards, expansion units, and storage drives are sold separately. Refer to the compatibility list for compatible devices. You will need two drives if you want to cache for both writing and reading -- so it's a good idea to get two. Synology’s productivity apps include the Office suite which is offered as a free alternative to Microsoft 365. It works with the Drive app to provide a central location for users to create documents, spreadsheets and presentations, collaborate on them together with others and keep them secure. After that, you can install them via the slot on the server's underside. The process is easy and painless. All you need is a small Philip-head screwdriver. Synology DS1821+: SSD caching upgrade

Overview

More caution is needed when selecting a 10GbE adapter, however, as Synology is rapidly shrinking its third-party hardware compatibility list and focusing more on its own solutions. When we installed the same Emulex dual-port 10GbE adapter we’d used to test the DS1618+, the DS1621+ hung during the boot phase and would only accept a dual-port Intel X520 10GbE adapter. Synology DiskStation DS1621+ review: 10GbE performance

It's even older than that -- Synology first announced it in 2020. But it's still going to be the latest Synology 8-bay NAS for homes and SMBs for a while -- Synology likely won't release its replacement this year.That amount is enough for general usage, but a memory upgrade is a must if you want to get the most out of the server. Synology hardware upgrades: Here's my new Synology DS1821+ and the upgrade parts, including a 10Gbps PCIe add-on card, a 32GB DDR4 RAM kit, and two 1.92GB Seagate IronWolf NVMe SSDs.

The 5-bay DX517 expansion unit uses an eSATA connection, which caps at 5Gbps, to connect to the server. However, the appropriate caching size depends on the server's storage volume that you want to cache. The Storage Manager app's SSD Cache Adviser function will give you a good idea of the cache size. By the way, you should only cache a hard drive volume. If you use SATA SSDs for storage, caching is unnecessary. On top of that, if you decide to cache, it's also a better idea to upgrade the server's network to 10Gbps -- more below -- or at least use its Link Aggregation feature to get a 2Gbps connection out of its two Gigabit ports. The DS1621 Digital Thermometer and Thermostat provides 9–bit temperature readings which indicate the temperature of the device. The thermal alarm output, TOUT, is active when the temperature of the device exceeds a user–defined temperature TH. The output remains active until the temperature drops below user defined temperature TL, allowing for any hysteresis necessary.

The performance you need

Creating M.2 storage pools requires the use of Synology-verified SSDs, which are rigorously tested under extreme temperature conditions. Thermal parameters for SSDs and NAS units are fine-tuned to ensure optimal management of thermal conditions under I/O-intensive environments. ( Learn more)

Our testing found the overall performance of the DS1621+ excellent, and it has plenty of grunt to run a wide variety of apps, host virtual machines, manage a IP camera system and more at the same time. The NAS was able to saturate a 1gBE connection no matter what else we had it doing, peaking at 729 Mbps reading and 710 Mbps writing. With the 10 GbE PCIe connection, it hit 3889 Mbps reading, and 2146Mbps writing, which is getting closer to the limits of the drive array. Considering you can find hard drives of 20TB and higher capacities nowadays, the number of drive bays is not that important. So, if one can live with fewer bays, the DS1821+ has nothing to justify the more expensive cost compared to the DS1621+. Hardware specifications: Synology DS1821+ vs DS1621+ Synology DS1821+ vs DS1621+: Hardware upgrades are (almost) a must You also get three USB 3.0 ports (one on the front) plus dual eSATAs. The latter is used for adding external drive bay expansions, and an extra 16 bays and 108TB total is possible. The NAS CPU itself has no fan on the heatsink, but the DS1621+ has dual rear 92mm fans that provide decent airflow, and keep your drive array from getting too hot. Synology SNV3400 series M.2 NVMe SSD drives can be installed through the built-in M.2 slots to enable SSD caching or create SSD storage pools. Drives are sold separately.

The DS1621+ comes populated with 4GB of ECC DDR4 in one slot of two slots, and can support up to 32GB. Despite the higher price, it’s great to see the ECC RAM used for improved protection against data corruption. Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermal sensitive system If you're using the DS1621+ and want to upgrade to the DS1821+ to take advantage of the two extra drive bays, the process is the same as when you migrate from one Synology server to another. User-defined temperature settings are stored in nonvolatile memory so parts may be programmed prior to insertion in a system. Temperature settings and temperature readings are all communicated to/from the DS1621 over a simple two–wire serial interface. The Dallas Semiconductor brand is no longer in use, but its products and technology continue to be a part of Maxim's portfolio.