PC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchCheck your NAS model, workload, and memory or cache statistics before buying anything. More RAM is the better candidate when memory is constrained or the system’s existing memory-backed cache is limiting performance. An SSD cache is worth considering only when the NAS supports it and your workload repeatedly reads the same data—especially random reads. It is unlikely to help much with one-pass transfers or large sequential media streams.
What RAM and SSD cache do
RAM supports the NAS operating system, services, and applications. On ZFS systems, it also holds the primary read cache, called the Adaptive Replacement Cache (ARC). An SSD cache is a separate, optional tier; in ZFS, L2ARC can hold additional read data beyond ARC.
L2ARC does not replace RAM. It uses memory for its operation and metadata: the TrueNAS Documentation Hub says the primary ARC needs a 96-byte entry for each L2ARC data block. Adding SSD cache to a memory-constrained system can therefore be the wrong fix.
These details describe ZFS and TrueNAS implementations, not every NAS platform. Other vendors’ cache features may work differently, so use the documentation for your exact model and software version.
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- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
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Match the upgrade to your workload
| Decision factor | More RAM | SSD cache |
|---|---|---|
| Primary role | Supports system services and applications; on ZFS, it can also expand the opportunity for RAM-backed ARC caching. | Adds a second-level read-cache tier on systems that support it. |
| Evidence to look for | Memory pressure, services or applications competing for memory, or a constrained first-level cache. | Frequent repeated random reads and a working set that outgrows RAM but can produce useful SSD-cache hits. |
| Key limitation | Supported memory type and capacity depend on the NAS model; there is no universal upgrade amount. | Model and software support, workload, and RAM use all matter. It may not help sequential or non-repeating reads. |
| Before buying | Check the model’s supported memory configuration and observe memory behavior during the slowdown. | Check exact cache support, drive compatibility, and cache hit/miss behavior under representative use. |
When more RAM is the stronger candidate
- The NAS is short on memory while running its operating system, apps, virtual machines, or other services.
- On ZFS, the primary ARC is the relevant limit; adding L2ARC does not correct inadequate system memory.
- You need capacity for system or application use, not only faster access to a subset of stored data.
When an SSD cache is the stronger candidate
- The NAS explicitly supports SSD caching or, for ZFS, the relevant L2ARC configuration.
- Your workload repeatedly accesses a relatively stable set of data, particularly through random reads.
- Measurements show that the cache is serving useful hits and the remaining delay is plausibly tied to storage reads.
Synology describes frequent random I/O and rereads as better candidates for SSD cache than large sequential operations such as HD video streaming. Reads that are entirely random, or data that is not usefully read again, also have limited benefit. TrueNAS likewise cautions that L2ARC effectiveness depends on the storage environment, workload, software, and performance goals; adding a cache device does not guarantee a gain.
Measure the NAS before choosing
- Identify the exact platform. Record the NAS make and model, operating system or DSM version, file system, RAM limits, supported memory modules, and cache options. Confirm that the proposed cache mode and drive interface are supported by that model.
- Describe what is slow. Note whether the slowdown occurs with repeated random reads, one-time file copies, media streaming, writes, or applications. A cache is most promising when the same active data is read repeatedly.
- Observe behavior during the slow period. On TrueNAS, inspect ARC size, requests, hits, misses, and hit ratio in its reporting tools; TrueNAS also documents
arc_summary.pyandarcstat.py. On Synology, check SSD cache status and hit rate in Storage Manager. - Relate cache statistics to the workload. A hit-rate figure is not itself a measure of speed improvement. Consider whether the workload is cache-friendly and whether the NAS remains slow on cache misses.
- Change one thing, then compare. After a RAM or cache change, run the same representative workload and compare the same measurements. A cache hit rate can rise without fixing a separate bottleneck in disk throughput, CPU, network, or application behavior.
How to interpret the platform guidance
TrueNAS and ZFS
The TrueNAS ZFS Primer advises against adding L2ARC when a system has less than 32 GiB of RAM, and says L2ARC size should not exceed ten times system RAM. Treat both figures as TrueNAS guidance for its ZFS context, not as universal requirements or NAS sizing laws. The TrueNAS Hardware Guide also emphasizes that memory needs depend on system services and workload.
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TrueNAS describes L2ARC as slower than system memory but faster than standard hard drives. That comparison does not establish how much faster a particular NAS workload will become. The cited documentation does not provide a broadly applicable performance percentage comparing a RAM upgrade with SSD cache.
Synology
Synology’s DSM 7 documentation provides a cache hit-rate calculation. For read-only cache, it is accelerated random read counts divided by total random read counts, multiplied by 100%. For read-write cache, it is accelerated random read and write counts divided by total random read and write counts, multiplied by 100%. Use the figure as an indicator of cache activity in context, not as a direct speedup percentage.
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
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- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
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Synology says cache support varies by NAS, and recommends checking the compatibility list for SSDs. It warns that an unlisted SSD may affect system stability and cause data loss. Do not assume a drive slot or connector alone means SSD cache is supported.
Quick Recap
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
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Rank #4
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Check compatibility before purchasing
- For RAM, verify the exact model’s supported memory type, capacity, and configuration.
- For SSD cache, verify that the NAS and software version support the cache feature and mode, then check the vendor’s drive compatibility guidance.
- For TrueNAS L2ARC, account for its RAM overhead and apply the platform’s own guidance rather than assuming cache is a substitute for memory.
- Do not select a universal RAM module or SSD based only on the NAS brand; compatibility can differ between models and generations.
Sources
- TrueNAS Documentation Hub: L2ARC
- TrueNAS Documentation Hub: ZFS Primer
- TrueNAS Documentation Hub: TrueNAS Hardware Guide
- Synology Knowledge Center: SSD Cache | DSM
- Synology Knowledge Center: Synology SSD Cache White Paper for DSM 7.1
- TrueNAS Documentation Hub: Reporting Screens
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