https://github.com/dividuum/fdb-nbd

A totally proof-of-concept FoundationDB based network block device backend
https://github.com/dividuum/fdb-nbd

foundationdb nbd python

Last synced: 3 months ago
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A totally proof-of-concept FoundationDB based network block device backend

• Host: GitHub
• URL: https://github.com/dividuum/fdb-nbd
• Owner: dividuum
• Created: 2018-04-28T18:07:06.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2018-04-30T08:23:58.000Z (over 6 years ago)
• Last Synced: 2024-07-31T20:35:18.554Z (5 months ago)
• Topics: foundationdb, nbd, python
• Language: Python
• Size: 10.7 KB
• Stars: 116
• Watchers: 11
• Forks: 7
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# A totally proof-of-concept FoundationDB based NBD backend

I wanted to play around with [FoundationDB](https://www.foundationdb.org/) a bit more and

building a [network block device (NBD)](https://nbd.sourceforge.io/) backend seemed like

a good fit for that.

**Do not use this in production**, unless you like data loss, kernel crashes and you don't

mind if your house burns down.

If you're interested in a more serious implementation, have a look at https://github.com/spullara/nbd.

## Installation

 * Install [FoundationDB](https://apple.github.io/foundationdb/local-dev.html).

 * Run `fdb-nbd.py`. It will start a local TCP server on port 10809 (default NBD port).

 * Load the `nbd` kernel module.

 * Run `nbd-client -N example 127.0.0.1 /dev/nbd0`. This will initialize the network block device `/dev/nbd0` and point it to the started python server.

 * You might now format `/dev/nbd0` with any filesystem and mount it.

## Cleaning up

 * Unmount your filesystem

 * Run `nbd-client -d /dev/nbd0` to disconnect the block device from the server

## Worth noting

 * The server can handle multiple block device "stores" at once. In the above example, `example` got selected with the `-N` argument of `nbd-client`. Have a look at the source code of `fdb-nbd.py` to see how this is initialized.

 * You can list all other available "stores" with `nbd-client -l 127.0.0.1`

 * The server is hardcoded to use a blocksize of `1024`. Each block is stored in its own FoundationDB key `('dev', 'example', 'blocks', block_nr)`. Partial reads or writes of blocks are not supported.

 * Since it's possible, I just compress/decompress each key before set/get. Yay.

 * It's interesting to see how block device caching works. File system actions often don't directly cause block device operations. Play around with `sync` and flushing the cache `echo 3 > /proc/sys/vm/drop_caches` for maximum effect.

 * Don't suddenly stop the server or disconnect with `nbd-client`. The kernel can be a bit sensitive about this. I've had unkillable processes as a result and a kernel OOPS. You have been warned.

 * Performance isn't too good, at least in my tests. It's around 10MB/s or so with a locally running FoundationDB. But hey: It works :-)