Memory pool or SSD cache?
In addition to the four SATA ports, the DS923 offers two M.2 2280 slots that can be used for either SSD caching or storage pools with NVMe SSDs, as the DS923 can now also use M.2 SSDs for this purpose. This is a first for Synology, as previous models only had M.2 slots for SSD caching. However, there is a very unpleasant and annoying catch, because only certain M.2 SSDs confirmed by Synology as suitable can be used for these storage pools. Thermal aspects might also play a role, since the installation location is not particularly optimal.
Thus, Synology only lists its own models as compatible, which is annoying, especially since only Synology SSDs with matching firmware are allowed to form an M.2 storage pool. So, the company cleverly sets clear limits here and promotes the purchase of its own products, which is not really customer-friendly and reminiscent of Apple. This is exactly the reason why I opted for the old familiar SSD cache after all.
When the installed M.2 SSDs serve as cache, there is the option to use them either as combined read/write cache or only as read cache. The read-only cache stores duplicates of frequently accessed files, which speeds up read processes without the risk of data loss since only copies are stored. When used as a combined cache, they are considered part of the NAS’s total storage. Therefore, the SSD cache must be disabled in the DSM before the SSDs can be removed. For security reasons, the cache can only be operated in RAID 1 mode.
So, an SSD cache in a NAS can speed up data access considerably, especially for frequently used data. SSDs are faster and more efficient compared to traditional HDDs, especially when dealing with small files. They also offer reduced latency, which means data is available almost immediately when requested. This is especially useful for applications that require fast data access. And it’s important to remember that my new SSD cache still requires plenty of 300 MB from the RAM, which once again justifies its upgrade.
However, there are also some considerations to take into account. SSDs tend to be more expensive than HDDs, and while they offer fast performance, they have a limited number of write cycles, which can affect their lifespan. It’s also important to note that not all data will benefit from the speed increase, as an SSD cache in a NAS is typically smaller than the main HDD storage. Thus, an SSD cache in a NAS can be beneficial in many situations, but it is also important to consider the cost, the lifespan of the SSD, and the specific requirements of the NAS system.
SSD installation and cooling tips
The two openings are located on the bottom of the NAS system. One can open the two covers without tools and insert the two SSDs. You should use identical SSDs for two SSDs, so that there are no allocation problems. Either use new SSDs or at least SSDs where the old partitions have been deleted. The old Ryzen only uses PCIe 3.0 anyway and the speed is less important here. SSDs with transfer rates of up to 3000 MB/s for reading and 1500 MB/s for writing are completely sufficient.
It is much more important that memory chips and controllers do not get too hot and you should definitely avoid QLC flash. It doesn’t last very long and the performance goes down faster than you can say pug. The two Gammix S70 Blade from XPG that I use are quite a good compromise with their 1 TB each. Nothing extremely overbred and provided with usable firmware. But curious as I am, I tested the temperatures again, because the few small air vents in the case covers are certainly not really helpful.
The trick for the comparison: One of the SSDs uses a glued-on aluminum cooler, the other remains naked. Both SSDs do not get above 55 °C even in continuous use when copying or indexing, whereby it only makes a difference of around 3 Kelvin when the cooler is used. That can also be left out. From this point of view, the thermal argument is actually none at all, and I remember the Apple ID again. If you want to use SSDs with taller heatsinks, which is quite possible, just omit the covers on the bottom. The feet are high enough. If you’re smart, you’d better put ultra-soft 3 mm pads between the memory modules and the PCB. That helps more than a small aluminum strip as a cooler.
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