1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
|
# bcachefs compression design:
Unlike other filesystems that typically do compression at the block level,
bcachefs does compression at the extent level - variable size chunks, up to (by
default) 128k.
When reading from extents that are compressed (or checksummed, or encrypted) we
always have to read the entire extent - but in return we get a better
compression ratio, smaller metadata, and better performance under typical workloads.
## Available options
The three currently supported algorithms are gzip, lz4, and zstd. Compression
may be enabled for the entire filesystem (e.g. at format time, or via the
options directory in sysfs), or on a specific file or directory via the
`bcachefs setattr` command.
### Compression level
The compression level may also be optionally specified, as an integer between 0
and 15, e.g. `lz4:15`. 0 specifies the default compression level, 1 specifies
the fastest and lowest compression ratio, and 15 the slowest and best
compression ratio.
### Background compression
If the `background_compression` option is used, data will be compressed (or
recompressed, with different options) in the background by the rebalance
thread. Like the `compression` option, `background_compression` may be set for
both the whole filesystem and on individual files or directories.
This lets more aggressive compression be used (e.g. `zstd:15`) without
bottlenecking foreground writes.
|
