The UGREEN UG-50857 (also sold as CM198) is a two-bay docking station that reads, writes, and clones SATA drives over USB 3.0. In practice, it does two jobs. First, it lets a computer access two bare hard drives or SSDs at once. Second, and more usefully, it clones one drive to another without a computer at all. Because of that offline clone function, the UG-50857 suits technicians and anyone upgrading storage.
Dock two drives, or clone without a computer
The UG-50857 has two SATA III 15-pin bays. Consequently, you can slot in two drives side by side. Connect the dock to a PC over USB 3.0, and both drives appear as normal storage for copying, backup, or bulk transfer. Alternatively, disconnect the USB cable entirely and use the CM198 as a standalone duplicator. In that mode, it copies the drive in the source bay to the drive in the target bay on its own.
How offline cloning works
Offline cloning is the headline feature. To use it, you place the source drive in Bay A and the target drive in Bay B, then start the clone with the button on the dock. From there, the UG-50857 performs a sector-by-sector copy while a row of LEDs shows progress. As a result, you can:
- Migrate data from an old drive to a new one.
- Transfer an operating system from an HDD to an SSD.
- Make a full backup image for safekeeping.
- Recover data from a bare drive standalone.
One practical rule applies, however. The target drive must be equal to or larger than the source, or the clone will not complete. Therefore, plan the drive sizes before you start.
USB 3.0 with UASP acceleration
For everyday docking, speed matters. The CM198 pairs a USB 3.0 (5Gbps) host link with an internal SATA III (6Gbps) path. In addition, it supports the UASP protocol. According to UGREEN’s own lab figures, UASP delivers roughly 70% faster reads and 40% faster writes than conventional USB 3.0. Meanwhile, a JMicron JMS561U chipset manages the transfer, which keeps throughput steady during large copies.
Drive support and capacity
The UG-50857 accepts both 2.5-inch and 3.5-inch SATA HDDs and SSDs, so it covers laptop drives, desktop drives, and solid-state drives alike. On capacity, current UGREEN listings state support for up to 20TB per bay, or 40TB combined. That headroom makes the dock a fit for large media libraries and archive drives.
Power, cooling, and auto-sleep
Because 3.5-inch drives need more current than USB alone can supply, the UG-50857 ships with a 12V / 3A external power adapter. Furthermore, the vertical, open design helps the drives shed heat during long sessions. To save energy, the dock also drops idle drives into sleep after about 15 minutes of inactivity. As a result, the drives run cooler and last longer.
LED indicators
Finally, front LEDs report status at a glance. They show power, drive activity, and — during a clone — the copy progress in stages. So you can walk away from a long clone and check the LEDs to see how far it has run.
Who is this best suited for
- IT technicians and repair shops — because the UG-50857 clones a drive with no computer attached, it speeds up HDD-to-SSD migrations and OS transfers on the bench or in the field.
- Users upgrading a laptop or desktop drive — offline cloning copies an existing system drive to a new SSD, so the CM198 turns a storage upgrade into a one-button job.
- Photographers, videographers, and data archivists — with 2.5″/3.5″ support and up to 40TB combined, the dock handles bulk cold storage and full-drive backups.
- Small offices running backups — two bays plus UASP-accelerated USB 3.0 make routine copy and mirror tasks quick and simple.
- Anyone with loose SATA drives — the UG-50857 gives instant USB access to bare HDDs and SSDs without opening a case.
