Why a drive letter and not an SFTP program
A graphical SFTP client is fine for moving files. A drive letter is for working on them in place: opening a spreadsheet from the server in Excel, pointing a backup tool or a script at S:\, editing a configuration file in your usual editor. Every Windows program understands a drive; few understand SFTP.
It also needs nothing new on the server. If you can ssh user@host, you can mount it — no Samba, no extra ports.
What you need
- Any server with SSH and the SFTP subsystem enabled — the default on OpenSSH for Linux, BSD and macOS, and on most NAS firmware.
- A login: a password, or better, an OpenSSH private key.
- Windows 10 or 11 (64-bit), or Windows Server 2019 or newer.
Mount it with Pier
- Download and run the Pier installer; it adds the Dokany file-system driver when it is missing.
- Open Pier from the tray icon and press Add. Choose the SFTP protocol.
- Enter the server name, the port (22 unless changed), the user and the root folder — for example
/home/useror/srv/data. - Choose password or key file. For a key, point to the private key, such as
C:\Users\you\.ssh\id_ed25519, and enter its passphrase if it has one. - Press Check. Pier logs in, tests writing and renaming and reports whether the server keeps timestamps and resumes uploads.
- Pick a drive letter and press OK.
Pier reads OpenSSH-format keys — Ed25519, ECDSA and RSA — directly. Keys in PuTTY's .ppk format need converting to OpenSSH format with PuTTYgen first.
What makes it usable on a slow link
- Block cache. File blocks are kept on your disk, so reading the same large file twice does not download it twice, and opening a big archive fetches only the parts that are read.
- Resume. An interrupted upload continues from the file offset where it stopped, not from zero.
- Parallel connections. A pool of SSH connections lets several transfers run at once; the number is yours to set.
- Reconnect. After a Wi-Fi change, a VPN drop or sleep the drive re-dials with back-off and finishes the queued writes.
Permissions and ownership
The drive acts as the SSH user you logged in with. Files you create belong to that user and get the server's default permissions (its umask). If a folder is read-only for that user on the server, it is read-only on the drive — the server check in Pier tells you so before you find out the hard way.
Other ways to do it
Open-source alternatives exist: SSHFS-Win on top of WinFsp, and rclone mount. They are good tools for people comfortable with a command line. Pier's difference is a managed Windows service with a settings window, a persistent block cache, a transfer queue you can see and automatic updates.