When comparing Helios4 vs Banana Pi M3, the Slant community recommends Helios4 for most people. In the question“What are the best single-board computers for building a NAS system?” Helios4 is ranked 4th while Banana Pi M3 is ranked 13th. The most important reason people chose Helios4 is:
Has four SATA 3.0 ports so it can handle up to 48TB of storage (12TB on each SATA port).
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Pros
Pro 4 X SATA 3.0
Has four SATA 3.0 ports so it can handle up to 48TB of storage (12TB on each SATA port).
Pro Official support for multiple Desktop-version Linux distros
Banana Pi officially supports Fedora, Arch, Lubuntu and openSUSE. It also can be used with Raspbian (Debian derivative) or Android.
Pro Excellent compatibility with Raspberry Pi software
Other than having a port of Raspbian (the official OS for Raspberry Pi) available for use with full capabilities, Banana Pi can also use many applications that were originally written for Raspberry. One of these is WiringPi, a C/C++ library which gives easy access to Raspberry's I/O with a strong Arduino flavor. But that is just one example of the many open source projects being ported to Banana Pi.
Cons
Con The project fall down
Con No battery or UPS
A PC tailored for NAS usage should have a battery or UPS to prevent data corruption after a power loss. A tiny battery to safely shut it down would be enough.
Con Company shut down business!
See their website-shop.
Con Expensive
After the preorder It is expensive now.
Con No off-the-shelf camera modules
The A20 chip that the Banana Pi uses lacks a true Camera Serial Interface implementation, instead it uses a parallel camera interface. The problem with this is that there are no off-the-shelf camera modules that support this and can connect to the Banana Pi, but it should be mentioned that the makers of Banana Pi have promised to create a camera module that is supported by it.
Con Expensive
It costs $129.99.