The Thecus Top Tower N8850 is definitely an impressive NAS device, both in terms of design and performance. The firmware perhaps has some rough edges, but it's complete enough. It makes the Thecus Top Tower N8850 an interesting option if you want high performance and don't mind that it makes a little noise. It's great that you can upgrade the N8850 by adding a 10 Gigabit adapter or increasing the amount of RAM.
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