Say you've got a big slow raid 6, and an ssd or three. Wouldn't it be
nice if you could use them as cache... Hence bcache.
-Wiki and git repositories are at:
+The bcache wiki can be found at:
+ https://bcache.evilpiepirate.org
- - https://bcache.evilpiepirate.org
- - http://evilpiepirate.org/git/linux-bcache.git
- - https://evilpiepirate.org/git/bcache-tools.git
+This is the git repository of bcache-tools:
+ https://git.kernel.org/pub/scm/linux/kernel/git/colyli/bcache-tools.git/
+
+The latest bcache kernel code can be found from mainline Linux kernel:
+ https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
It's designed around the performance characteristics of SSDs - it only allocates
in erase block sized buckets, and it uses a hybrid btree/log to track cached
to be flushed.
Getting started:
-You'll need make-bcache from the bcache-tools repository. Both the cache device
+You'll need bcache util from the bcache-tools repository. Both the cache device
and backing device must be formatted before use::
- make-bcache -B /dev/sdb
- make-bcache -C /dev/sdc
+ bcache make -B /dev/sdb
+ bcache make -C /dev/sdc
-make-bcache has the ability to format multiple devices at the same time - if
+`bcache make` has the ability to format multiple devices at the same time - if
you format your backing devices and cache device at the same time, you won't
have to manually attach::
- make-bcache -B /dev/sda /dev/sdb -C /dev/sdc
+ bcache make -B /dev/sda /dev/sdb -C /dev/sdc
+
+If your bcache-tools is not updated to latest version and does not have the
+unified `bcache` utility, you may use the legacy `make-bcache` utility to format
+bcache device with same -B and -C parameters.
bcache-tools now ships udev rules, and bcache devices are known to the kernel
immediately. Without udev, you can manually register devices like this::
If bcache is not available in the kernel, a filesystem on the backing
device is still available at an 8KiB offset. So either via a loopdev
of the backing device created with --offset 8K, or any value defined by
---data-offset when you originally formatted bcache with `make-bcache`.
+--data-offset when you originally formatted bcache with `bcache make`.
For example::
After you boot back with bcache enabled, you recreate the cache and attach it::
- host:~# make-bcache -C /dev/sdh2
+ host:~# bcache make -C /dev/sdh2
UUID: 7be7e175-8f4c-4f99-94b2-9c904d227045
Set UUID: 5bc072a8-ab17-446d-9744-e247949913c1
version: 0
The default metadata size in bcache is 8k. If your backing device is
RAID based, then be sure to align this by a multiple of your stride
- width using `make-bcache --data-offset`. If you intend to expand your
+ width using `bcache make --data-offset`. If you intend to expand your
disk array in the future, then multiply a series of primes by your
raid stripe size to get the disk multiples that you would like.