1.編譯安裝
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| # git clone http:///git/bcache-tools.git
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安裝前需要兩個依賴包pkg-config和libblkid-dev
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| # apt-get install pkg-config libblkid-dev
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然后編譯
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| # 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/
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2.使用方式
2.1 創(chuàng)建bcache設(shè)備
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| 命令：make-bcache -C <cache-device> -B <backing-device>
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以vde作為緩存盤，vdb和vdc作為后端設(shè)備創(chuàng)建bcache設(shè)備，有幾個后端設(shè)備就會生成幾個bcache設(shè)備。
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| # 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
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然后可以使用lsblk查看這些設(shè)備的對應(yīng)關(guān)系
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| # 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
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2.2 添加一塊后端設(shè)備（backing device）
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| 命令：make-bcache -B <backing-device>
# make-bcache -B /dev/vdh
UUID: bd1bc116-6f39-401e-a328-3bc0af4ac8d1
Set UUID: cd86812e-d24c-46da-b949-683969b59575
version: 1
block_size: 1
data_offset: 16
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接著看到對應(yīng)的設(shè)備是/dev/bcache3
查看cache set uuid
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| # 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
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“attach”后端設(shè)備
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| 命令：echo <cache set uuid> > /sys/block/bcache<N>/bcache/attach
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attach之后，緩存設(shè)備就能夠?qū)π录拥暮蠖嗽O(shè)備緩存數(shù)據(jù)了。
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| # echo 7681dbb3-6558-4e60-b062-5fbb648f6665 > /sys/block/bcache3/bcache/attach
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添加后使用lsblk查看
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| # 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
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2.3 刪除一塊后端設(shè)備
1）detach backing device
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| 命令：echo <cache set uuid> > /sys/block/bcache<N>/bcache/detach
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detach后端設(shè)備后，對應(yīng)的bcache設(shè)備還是存在的，只不過這個bcache設(shè)備是無緩存的，查看其狀態(tài)可以看到是no cache
比如刪除bcache3
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| # 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
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2)stop backing device
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| 命令：echo 1 > /sys/block/bcache<N>/bcache/stop
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detach后端設(shè)備后，對應(yīng)的bcache設(shè)備還存在，如果要刪除，還需要stop該設(shè)備
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| # 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
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2.4 新增一塊緩存設(shè)備（caching device）
1）創(chuàng)建cache設(shè)備
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| 命令：make-bcache -C <cache device>
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有可能對應(yīng)的設(shè)備已經(jīng)有一些元數(shù)據(jù)，需要使用wipefs清理掉
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| # 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
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2）與bcache設(shè)備關(guān)聯(lián)
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| 命令：echo <cache set uuid> > /sys/block/bcache<N>/bcache/attach
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緩存設(shè)備需要與bcache設(shè)備關(guān)聯(lián)后，才能作為對應(yīng)bcache設(shè)備緩存。
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| # 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
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2.5 刪除cache設(shè)備
首先確保沒有backing device在使用它，上述的“刪除一塊后端設(shè)備”有說明如何設(shè)置取消后端設(shè)備對緩存設(shè)備的使用。
然后可以使用lsblk來查看是否有盤在引用它。
在在/sys/fs/bcache目錄下還有對應(yīng)的cache set uuid，unregister該set uuid后這個cache設(shè)備就被視為刪除了。
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| 命令：echo 1 > /sys/fs/bcache/<cache set uuid>/unregister
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比如vde已經(jīng)不作為任何設(shè)備的緩存盤了，在/sys/fs/bcache目錄下有對應(yīng)的cache set uuid
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| # 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
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然后unregister掉該cache設(shè)備
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| #echo 1 > /sys/fs/bcache/[SSD bcache UUID]/unregister
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然后再看/sys/fs/bcache目錄下已經(jīng)沒有這個cache設(shè)備的uuid了
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| # 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
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2.6 參數(shù)調(diào)節(jié)
1）設(shè)置緩存模式
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| 命令：echo <cache mode> > /sys/block/bcache<N>/bcache/cache_mode
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可以為不同的bcache設(shè)備設(shè)置不同的緩存策略
并且設(shè)置了緩存策略后，機器重啟后仍然生效。
另外，機器重啟后，bcache設(shè)備也能自動重建出來。
bcache還有其他可以調(diào)節(jié)的參數(shù)，這里不作說明，具體參考官方說明。
