1.编译安装
1 | # git clone http://evilpiepirate.org/git/bcache-tools.git |
安装前需要两个依赖包pkg-config和libblkid-dev1
# apt-get install pkg-config libblkid-dev
然后编译1
2
3
4
5
6
7
8
9
10
11
12
13# make
cc -O2 -Wall -g `pkg-config --cflags uuid blkid` make-bcache.c bcache.o `pkg-config --libs uuid blkid` -o make-bcache
cc -O2 -Wall -g `pkg-config --cflags uuid blkid` probe-bcache.c `pkg-config --libs uuid blkid` -o probe-bcache
cc -O2 -Wall -g -std=gnu99 bcache-super-show.c bcache.o `pkg-config --libs uuid` -o bcache-super-show
# make install
install -m0755 make-bcache bcache-super-show /usr/sbin/
install -m0755 probe-bcache bcache-register /lib/udev/
install -m0644 69-bcache.rules /lib/udev/rules.d/
install -T -m0755 initramfs/hook /usr/share/initramfs-tools/hooks/bcache
if [ -d /lib/dracut/modules.d ]; \
then install -D -m0755 dracut/module-setup.sh /lib/dracut/modules.d/90bcache/module-setup.sh; \
fi
install -m0644 -- *.8 /usr/share/man/man8/
2.使用方式
2.1 创建bcache设备
1 | 命令：make-bcache -C <cache-device> -B <backing-device> |
以vde作为缓存盘，vdb和vdc作为后端设备创建bcache设备，有几个后端设备就会生成几个bcache设备。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# make-bcache -C /dev/vde -B /dev/vdb /dev/vdc
UUID: 8941a5d1-074e-4cc6-a6dd-56cb1f65aed3
Set UUID: 7681dbb3-6558-4e60-b062-5fbb648f6665
version: 0
nbuckets: 20480
block_size: 1
bucket_size: 1024
nr_in_set: 1
nr_this_dev: 0
first_bucket: 1
UUID: 9e28d09b-942d-487e-be22-9132063da572
Set UUID: 7681dbb3-6558-4e60-b062-5fbb648f6665
version: 1
block_size: 1
data_offset: 16
UUID: 1bacf83e-2754-4d6a-a964-09e53e6e679f
Set UUID: 7681dbb3-6558-4e60-b062-5fbb648f6665
version: 1
block_size: 1
data_offset: 16
root@nbsagent3:~# ls /dev/b
bcache0 bcache1 block/ btrfs-control bus/
root@nbsagent3:~# ls /dev/bcache* -la
brw-rw---T 1 root disk 250, 0 5月 22 17:23 /dev/bcache0
brw-rw---T 1 root disk 250, 1 5月 22 17:23 /dev/bcache1
然后可以使用lsblk查看这些设备的对应关系1
2
3
4
5
6
7
8
9
10
11
12
13# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 254:0 0 20G 0 disk
└─vda1 254:1 0 20G 0 part /
vdb 254:16 0 50G 0 disk
└─bcache1 250:1 0 50G 0 disk
vdc 254:32 0 50G 0 disk
└─bcache0 250:0 0 50G 0 disk
vdd 254:48 0 50G 0 disk
└─bcache2 250:2 0 50G 0 disk
vde 254:64 0 10G 0 disk
├─bcache0 250:0 0 50G 0 disk
└─bcache1 250:1 0 50G 0 disk
2.2 添加一块后端设备（backing device）
1 | 命令：make-bcache -B <backing-device> |
接着看到对应的设备是/dev/bcache3
查看cache set uuid1
2
3
4
5
6
7# ls -la /sys/fs/bcache/
total 0
drwxr-xr-x 3 root root 0 May 22 17:23 .
drwxr-xr-x 6 root root 0 May 22 17:21 ..
drwxr-xr-x 7 root root 0 May 22 17:26 7681dbb3-6558-4e60-b062-5fbb648f6665
--w------- 1 root root 4096 May 22 17:57 register
--w------- 1 root root 4096 May 22 20:44 register_quiet
“attach”后端设备1
命令：echo <cache set uuid> > /sys/block/bcache<N>/bcache/attach
attach之后，缓存设备就能够对新加的后端设备缓存数据了。1
# echo 7681dbb3-6558-4e60-b062-5fbb648f6665 > /sys/block/bcache3/bcache/attach
添加后使用lsblk查看1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 254:0 0 20G 0 disk
└─vda1 254:1 0 20G 0 part /
vdb 254:16 0 50G 0 disk
└─bcache1 250:1 0 50G 0 disk
vdc 254:32 0 50G 0 disk
└─bcache0 250:0 0 50G 0 disk
vdd 254:48 0 50G 0 disk
└─bcache2 250:2 0 50G 0 disk
vde 254:64 0 10G 0 disk
├─bcache0 250:0 0 50G 0 disk
├─bcache2 250:2 0 50G 0 disk
└─bcache3 250:3 0 30G 0 disk
vdf 254:80 0 10G 0 disk
vdg 254:96 0 20G 0 disk
vdh 254:112 0 30G 0 disk
└─bcache3 250:3 0 30G 0 disk
2.3 删除一块后端设备
1）detach backing device
1 | 命令：echo <cache set uuid> > /sys/block/bcache<N>/bcache/detach |
detach后端设备后，对应的bcache
比如删除bcache31
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20# echo 7681dbb3-6558-4e60-b062-5fbb648f6665 > /sys/block/bcache3/bcache/detach
# cat /sys/block/bcache3/bcache/state
no cache
# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 254:0 0 20G 0 disk
└─vda1 254:1 0 20G 0 part /
vdb 254:16 0 50G 0 disk
└─bcache1 250:1 0 50G 0 disk
vdc 254:32 0 50G 0 disk
└─bcache0 250:0 0 50G 0 disk
vdd 254:48 0 50G 0 disk
└─bcache2 250:2 0 50G 0 disk
vde 254:64 0 10G 0 disk
├─bcache0 250:0 0 50G 0 disk
└─bcache2 250:2 0 50G 0 disk
vdf 254:80 0 10G 0 disk
vdg 254:96 0 20G 0 disk
vdh 254:112 0 30G 0 disk
└─bcache3 250:3 0 30G 0 disk
2)stop backing device
1 | 命令：echo 1 > /sys/block/bcache<N>/bcache/stop |
detach后端设备后，对应的bcache设备还存在，如果要删除，还需要stop该设备1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22# echo 1 > /sys/block/bcache3/bcache/stop
# ls /dev/bcache* -la
brw-rw---T 1 root disk 250, 0 May 22 17:51 /dev/bcache0
brw-rw---T 1 root disk 250, 1 May 22 17:54 /dev/bcache1
brw-rw---T 1 root disk 250, 2 May 22 20:42 /dev/bcache2
# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 254:0 0 20G 0 disk
└─vda1 254:1 0 20G 0 part /
vdb 254:16 0 50G 0 disk
└─bcache1 250:1 0 50G 0 disk
vdc 254:32 0 50G 0 disk
└─bcache0 250:0 0 50G 0 disk
vdd 254:48 0 50G 0 disk
└─bcache2 250:2 0 50G 0 disk
vde 254:64 0 10G 0 disk
├─bcache0 250:0 0 50G 0 disk
├─bcache1 250:1 0 50G 0 disk
└─bcache2 250:2 0 50G 0 disk
vdf 254:80 0 10G 0 disk
vdg 254:96 0 20G 0 disk
vdh 254:112 0 30G 0 disk
2.4 新增一块缓存设备（caching device）
1）创建cache设备
1 | 命令：make-bcache -C <cache device> |
有可能对应的设备已经有一些元数据，需要使用wipefs清理掉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
34
35
36
37
38
39
40
41
42
43
44# make-bcache -C /dev/vdf
Device /dev/vdf already has a non-bcache superblock, remove it using wipefs and wipefs -a
# wipefs -a /dev/vdf
4 bytes were erased at offset 0x27fff0000 (linux_raid_member)
they were: fc 4e 2b a9
# make-bcache -C /dev/vdf
UUID: 1f8bc71f-0106-4da5-b781-5de7b1517706
Set UUID: 7bfb0d17-b6d0-4fe9-942b-a1c75a0893ab
version: 0
nbuckets: 20480
block_size: 1
bucket_size: 1024
nr_in_set: 1
nr_this_dev: 0
first_bucket: 1
# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 254:0 0 20G 0 disk
└─vda1 254:1 0 20G 0 part /
vdb 254:16 0 50G 0 disk
└─bcache1 250:1 0 50G 0 disk
vdc 254:32 0 50G 0 disk
└─bcache0 250:0 0 50G 0 disk
vdd 254:48 0 50G 0 disk
└─bcache2 250:2 0 50G 0 disk
vde 254:64 0 10G 0 disk
├─bcache0 250:0 0 50G 0 disk
├─bcache1 250:1 0 50G 0 disk
└─bcache2 250:2 0 50G 0 disk
vdf 254:80 0 10G 0 disk
vdg 254:96 0 20G 0 disk
vdh 254:112 0 30G 0 disk
└─bcache3 250:3 0 30G 0 disk
nbsram_a 251:0 0 16M 0 disk
nbsram_b 251:16 0 16M 0 disk
nbsram_c 251:32 0 16M 0 disk
# ls /sys/fs/bcache/ -la
total 0
drwxr-xr-x 4 root root 0 May 22 17:23 .
drwxr-xr-x 6 root root 0 May 22 17:21 ..
drwxr-xr-x 7 root root 0 May 22 17:26 7681dbb3-6558-4e60-b062-5fbb648f6665
drwxr-xr-x 7 root root 0 May 22 21:05 7bfb0d17-b6d0-4fe9-942b-a1c75a0893ab
--w------- 1 root root 4096 May 22 17:57 register
--w------- 1 root root 4096 May 22 21:05 register_quiet
2）与bcache设备关联
1 | 命令：echo <cache set uuid> > /sys/block/bcache<N>/bcache/attach |
缓存设备需要与bcache设备关联后，才能作为对应bcache设备缓存。1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20# echo 7bfb0d17-b6d0-4fe9-942b-a1c75a0893ab > /sys/block/bcache3/bcache/attach
# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 254:0 0 20G 0 disk
└─vda1 254:1 0 20G 0 part /
vdb 254:16 0 50G 0 disk
└─bcache1 250:1 0 50G 0 disk
vdc 254:32 0 50G 0 disk
└─bcache0 250:0 0 50G 0 disk
vdd 254:48 0 50G 0 disk
└─bcache2 250:2 0 50G 0 disk
vde 254:64 0 10G 0 disk
├─bcache0 250:0 0 50G 0 disk
├─bcache1 250:1 0 50G 0 disk
└─bcache2 250:2 0 50G 0 disk
vdf 254:80 0 10G 0 disk
└─bcache3 250:3 0 30G 0 disk
vdg 254:96 0 20G 0 disk
vdh 254:112 0 30G 0 disk
└─bcache3 250:3 0 30G 0 disk
2.5 删除cache设备
首先确保没有backing device在使用它，上述的“删除一块后端设备”有说明如何设置取消后端设备对缓存设备的使用。
然后可以使用lsblk来查看是否有盘在引用它。
在在/sys/fs/bcache目录下还有对应的cache set uuid，unregister该set uuid后这个cache设备就被视为删除了。1
命令：echo 1 > /sys/fs/bcache/<cache set uuid>/unregister
比如vde已经不作为任何设备的缓存盘了，在/sys/fs/bcache目录下有对应的cache set uuid1
2
3
4
5
6
7
8# ls /sys/fs/bcache/ -la
total 0
drwxr-xr-x 4 root root 0 5月 26 09:07 .
drwxr-xr-x 6 root root 0 5月 26 09:06 ..
drwxr-xr-x 7 root root 0 5月 26 09:07 7681dbb3-6558-4e60-b062-5fbb648f6665
drwxr-xr-x 7 root root 0 5月 26 09:07 7bfb0d17-b6d0-4fe9-942b-a1c75a0893ab
--w------- 1 root root 4096 5月 26 09:07 register
--w------- 1 root root 4096 5月 26 09:06 register_quiet
然后unregister掉该cache设备1
#echo 1 > /sys/fs/bcache/[SSD bcache UUID]/unregister
然后再看/sys/fs/bcache目录下已经没有这个cache设备的uuid了1
2
3
4
5
6
7# ls /sys/fs/bcache/ -la
total 0
drwxr-xr-x 3 root root 0 5月 26 09:07 .
drwxr-xr-x 6 root root 0 5月 26 09:06 ..
drwxr-xr-x 7 root root 0 5月 26 09:07 7bfb0d17-b6d0-4fe9-942b-a1c75a0893ab
--w------- 1 root root 4096 5月 26 09:07 register
--w------- 1 root root 4096 5月 26 09:06 register_quiet
2.6 参数调节
1）设置缓存模式
1 | 命令：echo <cache mode> > /sys/block/bcache<N>/bcache/cache_mode |
可以为不同的bcache设备设置不同的缓存策略
并且设置了缓存策略后，机器重启后仍然生效。
另外，机器重启后，bcache设备也能自动重建出来。
bcache还有其他可以调节的参数，这里不作说明，具体参考官方说明。
3.参考资料
http://bcache.evilpiepirate.org/
http://lwn.net/Articles/550207/
http://blog.csdn.net/liumangxiong/article/details/18090043
http://unix.stackexchange.com/questions/115764/how-to-remove-cache-device-from-bcache
http://pommi.nethuis.nl/ssd-caching-using-linux-and-bcache/