Raspberry Pi: Transform the popular single-board computer into a NAS with up to four hard drives
A new NAS for the Raspberry Pi has emerged from a company called Wiretrustee. The Wiretrustee carrier board utilises the Compute Module 4 (CM4), which is currently the smallest fully-functioning Raspberry Pi 4 that the Pi Foundation sells. A Marvell 88SE9215 chip lies at the heart of the carrier board and is one that Wiretrustee has used to turns the CM4's PCIe connection into four SATA connector.
Correspondingly, the carrier board allows you to connect up to four SATA HDDs or SSDs to the CM4, each with a 220 MB/s peak write speed, albeit not simultaneously. The developer explained on Reddit that they were not:
...chasing high IO therefore a limitation of PCIe x1 wasn't a real problem to me. I still think you could have a decent speed with only one lane especially for my case where I anyway will connect and download/upload files from/to the home network via the internet.
However, the carrier board also relies on Gigabit Ethernet, which is a further limitation. With that said, the current price of SATA drives means that the carrier board should be cheaper to set-up than many DIY NAS units based on M.2 storage. Likewise, it should be possible to connect high storage volumes to the carrier board cheaply.
Moreover, Wiretrustee has included a physical HDMI 2.0 port, a USB Type-C port for power and two USB 2.0 Type-A ports. Additionally, the carrier board has a 12V 4-pin fan header, an RTC battery and a microSD card slot. The board itself measures 100 x 100 mm, which appears to be an efficient use of space. Wiretrustee is yet to finalise its carrier board, but it hopes to eventually bring the device to Crowd Supply. You can get involved with design choices on the accompanying Reddit thread.