Catfs is a caching filesystem written in Rust.
Overview
Catfs allows you to have cached access to another (possibily remote) filesystem. Caching semantic is read-ahead and write-through (see Current Status). Currently it only provides a data cache and all metadata operations hit the source filesystem.
Catfs is ALPHA software. Don't use this if you value your data.
Installation
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On Linux, install via pre-built binaries. You may also need to install fuse-utils first.
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Or build from source which requires Cargo.
:~/catfs$ cargo build
$ # debug binary now in ./target/debug/catf
:~/catfs$ cargo install
$ # optimized binary now in $HOME/.cargo/bin/catfs
Usage
Catfs requires extended attributes (xattr) to be enabled on the
filesystem where files are cached to. Typically this means you need to
have user_xattr mount option turned on.
$ catfs <from> <to> <mountpoint>
Catfs will expose files in <from> under <mountpoint>, and cache
them to <to> as they are accessed.
Benchmark
Compare using catfs to cache sshfs vs sshfs only. Topology is laptop - 802.11n - router - 1Gbps wired - desktop. Laptop has SSD whereas desktop has spinning rust.
Compare running catfs with two local directories on the same filesystem with direct access. This is not a realistic use case but should give you an idea of the worst case slowdown.
Write is twice as slow as expected since we are writing twice the amount.
To run the benchmark, do:
$ sudo docker run -e SSHFS_SERVER=user@host --rm --privileged --net=host -v $PWD/target:/root/catfs/target kahing/catfs-bench
# result is written to $PWD/target
The docker container will need to be able to ssh to user@host. Typically I arrange that by mounting the ssh socket from the host
$ sudo docker run -e SSHFS_OPTS="-o ControlPath=/root/.ssh/sockets/%r@%h_%p -o ControlMaster=auto -o StrictHostKeyChecking=no -o Cipher=arcfour user@host:/tmp" -e SSHFS_SERVER=user@host --rm --privileged --net=host -v $HOME/.ssh/sockets:/root/.ssh/sockets -v $PWD/target:/root/catfs/target kahing/catfs-bench
License
Copyright (C) 2017 Ka-Hing Cheung
Licensed under the Apache License, Version 2.0
Current Status
Catfs is ALPHA software. Don't use this if you value your data.
Entire file is cached if it's open for read, even if nothing is actually read.
Data is first written to the cache and the entire file is always
written back to the original filesystem on close(), so effectively
it's a write-through cache. Note that even changing one byte will
cause the entire file to be re-written.
Paging in/writeback are done in background threads. All other requests are serviced on the same thread, so many operations could block each other.
TODO
- move all operations to background threads