root@utumno:~# fio ~/rw4k
randwrite: (g=0): rw=randwrite, bs=4K-4K/4K-4K, ioengine=libaio, iodepth=64
fio 1.59
Starting 1 process
Jobs: 1 (f=1): [w] [100.0% done] [0K/49885K /s] [0 /12.2K iops] [eta 00m:00s]
randwrite: (groupid=0, jobs=1): err= 0: pid=1770
write: io=8192.3MB, bw=47666KB/s, iops=11916 , runt=175991msec
cpu : usr=4.33%, sys=14.28%, ctx=2071968, majf=0, minf=19
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.1%, >=64=0.0%
issued r/w/d: total=0/2097215/0, short=0/0/0
Run status group 0 (all jobs):
WRITE: io=8192.3MB, aggrb=47666KB/s, minb=48810KB/s, maxb=48810KB/s, mint=175991msec, maxt=175991msec
Disk stats (read/write):
sdb: ios=69/2097888, merge=0/3569, ticks=0/11243992, in_queue=11245600, util=99.99%
root@utumno:~# fio ~/rw4k
randwrite: (g=0): rw=randwrite, bs=4K-4K/4K-4K, ioengine=libaio, iodepth=64
fio 1.59
Starting 1 process
Jobs: 1 (f=1): [w] [100.0% done] [0K/75776K /s] [0 /18.5K iops] [eta 00m:00s]
randwrite: (groupid=0, jobs=1): err= 0: pid=1914
write: io=8192.3MB, bw=83069KB/s, iops=20767 , runt=100987msec
cpu : usr=3.17%, sys=13.27%, ctx=456026, majf=0, minf=19
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.1%, >=64=0.0%
issued r/w/d: total=0/2097215/0, short=0/0/0
Run status group 0 (all jobs):
WRITE: io=8192.3MB, aggrb=83068KB/s, minb=85062KB/s, maxb=85062KB/s, mint=100987msec, maxt=100987msec
Disk stats (read/write):
bcache0: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%
IO depth of 32: bcache 20.3k iops, raw ssd 19.8k iops
IO depth of 16: bcache 16.7k iops, raw ssd 23.5k iops
IO depth of 8: bcache 8.7k iops, raw ssd 14.9k iops
IO depth of 4: bcache 8.9k iops, raw ssd 19.7k iops
IO depth of 64: bcache 29.5k iops, raw ssd 25.4k iops
IO depth of 16: bcache 28.2k iops, raw ssd 27.6k iops
# cat /usr/lib/udev/rules.d/61-bcache.rules
....
# Backing devices: scan, symlink, register
IMPORT{program}="/sbin/blkid -o udev $tempnode"
# blkid and probe-bcache can disagree, in which case don't register
ENV{ID_FS_TYPE}=="?*", ENV{ID_FS_TYPE}!="bcache", GOTO="bcache_backing_end"
...
# lsblk -o NAME,MAJ:MIN,RM,SIZE,TYPE,FSTYPE,MOUNTPOINT,UUID,PARTUUID
NAME MAJ:MIN RM SIZE TYPE FSTYPE MOUNTPOINT UUID PARTUUID
sda 8:0 0 111.8G disk
├─sda1 8:1 0 3G part vfat /esp 7E67-C0BB d39828e8-4880-4c85-9ec0-4255777aa35b
└─sda2 8:2 0 108.8G part ext2 93d22899-cd86-4815-b6d0-d72006201e75 baf812f4-9b80-42c4-b7ac-5ed0ed19be65
sdb 8:16 0 931.5G disk
└─sdb1 8:17 0 931.5G part ntfs FAD2B75FD2B71EB7 90c80e9d-f31a-41b4-9d4d-9b02029402b2
sdc 8:32 0 2.7T disk bcache 4bd63488-e1d7-4858-8c70-a35a5ba2c452
└─bcache1 254:1 0 2.7T disk btrfs 2ff19aaf-852e-4c58-9eee-3daecbc6a5a1
sdd 8:48 0 2.7T disk bcache ce6de517-7538-45d6-b8c4-8546f13f76c1
└─bcache0 254:0 0 2.7T disk btrfs 2ff19aaf-852e-4c58-9eee-3daecbc6a5a1
sde 8:64 1 14.9G disk
└─sde1 8:65 1 14.9G part ext4 / d07321b2-b67d-4daf-8022-f3307b605430 5d0a4d76-115f-4081-91ed-fb09aa2318d
# make-bcache -B /dev/sdc /dev/sdd -C /dev/sda2
# dd if=/dev/zero count=1 bs=1024 seek=1 of=/dev/sda2
# lsblk -o NAME,MAJ:MIN,RM,SIZE,TYPE,FSTYPE,MOUNTPOINT,UUID,PARTUUID
NAME MAJ:MIN RM SIZE TYPE FSTYPE MOUNTPOINT UUID PARTUUID
sda 8:0 0 111.8G disk
├─sda1 8:1 0 3G part vfat /esp 7E67-C0BB d39828e8-4880-4c85-9ec0-4255777aa35b
└─sda2 8:2 0 108.8G part bcache 93d22899-cd86-4815-b6d0-d72006201e75 baf812f4-9b80-42c4-b7ac-5ed0ed19be65
├─bcache0 254:0 0 2.7T disk btrfs 2ff19aaf-852e-4c58-9eee-3daecbc6a5a1
└─bcache1 254:1 0 2.7T disk btrfs 2ff19aaf-852e-4c58-9eee-3daecbc6a5a1
sdb 8:16 0 931.5G disk
└─sdb1 8:17 0 931.5G part ntfs FAD2B75FD2B71EB7 90c80e9d-f31a-41b4-9d4d-9b02029402b2
sdc 8:32 0 2.7T disk bcache 4bd63488-e1d7-4858-8c70-a35a5ba2c452
└─bcache1 254:1 0 2.7T disk btrfs 2ff19aaf-852e-4c58-9eee-3daecbc6a5a1
sdd 8:48 0 2.7T disk bcache ce6de517-7538-45d6-b8c4-8546f13f76c1
└─bcache0 254:0 0 2.7T disk btrfs 2ff19aaf-852e-4c58-9eee-3daecbc6a5a1
sde 8:64 1 14.9G disk
└─sde1 8:65 1 14.9G part ext4 / d07321b2-b67d-4daf-8022-f3307b605430 5d0a4d76-115f-4081-91ed-fb09aa2318dd