Do I need a filesystem driver on both machines?

No. Only the machine that mounts needs WinFsp, fuse3 or macFUSE. The serving side runs one user space binary with no kernel driver.

KEIBIDROP and sshfs

Q: Why is sshfs slow over a high latency link?

SFTP reads in small requests and waits for each one, so throughput is set by round trip time rather than by bandwidth. Measured across a 200 ms link, sshfs moved about 326 KB per round trip and held 1.33 MB/s at both 100 MB and 1 GB file sizes.

Q: Does KeibiDrop need inbound SSH?

No. Both peers dial out and a relay bridges NAT, so no inbound port is opened on either network.

Same idea. Different behaviour once the link gets long.

By Marius-Florin Cristian · 18 August 2026

On a 200 ms link, sshfs measured 1.33 MB/s at 100 MB and 1.33 MB/s at 1 GB. A rate that does not move with file size is a latency bound. KEIBIDROP read 20 to 30 MB/s on the same link.

The measurement

Timisoara VPS reading a Singapore Windows Server, clean datacenter path, about 200 ms round trip. OpenSSH with chacha20-poly1305, compression off, otherwise defaults. Cold client per trial with caches dropped, sequential dd read.

File size	sshfs	Trials
100 MB	1.32 to 1.34 MB/s, median 1.33	n=10
1 GB	1.33 MB/s	n=5
Same link, KEIBIDROP on demand	20 to 30 MB/s

At 1.33 MB/s across a 245 ms round trip, about 326 KB crosses per round trip. Throughput follows the number of round trips, so a faster line does not help.

Side by side

	KEIBIDROP	sshfs
Inbound port on the target	None	SSH
Windows target	Native	Needs sshd installed
Windows client	Native, WinFsp	Third party ports
Long link	Read-ahead hides round trips	One round trip per small read
After a drop	Resumes per chunk	Reconnects with `-o reconnect`
Re-reading an edited file	Changed regions only	Whole file
Encryption	End to end, hybrid post-quantum	SSH transport
Filesystem driver	On the mounting side	On the mounting side
Appliance with no shell	No	Yes, if it runs sshd
Already installed everywhere	No	Yes, on Linux

Editing across the mount

Reading is half of it. When a file changes at the source, the question is how many bytes move again.

Over loopback, a 2 MB in place change at an unaligned offset inside a 1 GB file moved 18.56 MB, verified byte exact by sha256. The same change in a 256 MB file moved 16.02 MB. The floor is about 16 MB, so the proportion improves with file size.

rsync in default whole file mode sent 268.5 MB for that change. rsync has a delta mode, but pointed at a mounted path it treats the file as local and skips the delta algorithm, and its checksum pass reads the whole file back through the mount.

Limits

A driver on the mounting side. WinFsp, fuse3 or macFUSE on whichever machine mounts. The serving side needs none.
Appliances need a jump host. ESXi and network appliances run no new binaries. Mount the datastore on a Linux box you can run on, and share that out.
Two peers per connection. A share joins two machines rather than a fleet.

Common questions

Why is sshfs slow over a high latency link?

SFTP reads in small requests and waits for each one. The flat rate across file sizes above is that effect measured directly.

Does a faster connection fix it?

No. The limit is the number of round trips, so extra bandwidth goes unused.

Do I need a driver on both machines?

No. Only the side that mounts. The serving side runs one user space binary.

Does KEIBIDROP need inbound SSH?

No. Both peers dial out and a relay bridges NAT.

Remote triage without a VPN · Share a folder read only · Install