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bcache: doc: update Documentation/admin-guide/bcache.rst

Browse Source 
bcache.rst is from the original bcache.txt which was merged in mainline
kernel v3.10. There are a few things changed in the past 7 years. This
patch updates bache.rst documents in following content,
- Update bcache-tools git repo to,
  https://git.kernel.org/pub/scm/linux/kernel/git/colyli/bcache-tools.git/
- Update bcache kernel tree to mainline kernel tree,
  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
- make-bcache util is replaced by the unified bcache util,
  `make-bcache` now can be performed by `bcache make`

Signed-off-by: Coly Li <colyli@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Link: https://lore.kernel.org/r/20200821151354.16727-1-colyli@suse.de
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Coly Li
2020-08-21 23:13:54 +08:00
committed by Jonathan Corbet
parent bb84bc51d2
commit 27c8700bd1
1 changed files with 19 additions and 12 deletions
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31
Documentation/admin-guide/bcache.rst
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@@ -5,11 +5,14 @@ A block layer cache (bcache)
Say you've got a big slow raid 6, and an ssd or three. Wouldn't it be 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. 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 This is the git repository of bcache-tools:
- http://evilpiepirate.org/git/linux-bcache.git https://git.kernel.org/pub/scm/linux/kernel/git/colyli/bcache-tools.git/
- https://evilpiepirate.org/git/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 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 in erase block sized buckets, and it uses a hybrid btree/log to track cached
@@ -41,17 +44,21 @@ in the cache it first disables writeback caching and waits for all dirty data
to be flushed. to be flushed.
Getting started: 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:: and backing device must be formatted before use::
make-bcache -B /dev/sdb bcache make -B /dev/sdb
make-bcache -C /dev/sdc 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 you format your backing devices and cache device at the same time, you won't
have to manually attach:: 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 bcache-tools now ships udev rules, and bcache devices are known to the kernel
immediately. Without udev, you can manually register devices like this:: immediately. Without udev, you can manually register devices like this::
@@ -188,7 +195,7 @@ D) Recovering data without bcache:
If bcache is not available in the kernel, a filesystem on the backing 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 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 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:: For example::
@@ -210,7 +217,7 @@ E) Wiping a cache device
After you boot back with bcache enabled, you recreate the cache and attach it:: 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 UUID: 7be7e175-8f4c-4f99-94b2-9c904d227045
Set UUID: 5bc072a8-ab17-446d-9744-e247949913c1 Set UUID: 5bc072a8-ab17-446d-9744-e247949913c1
version: 0 version: 0
@@ -318,7 +325,7 @@ want for getting the best possible numbers when benchmarking.
The default metadata size in bcache is 8k. If your backing device is 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 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 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. raid stripe size to get the disk multiples that you would like.