Hi Kent,
I have configured Bcache as follows:
echo /dev/sda3 > /sys/fs/bcache/register
echo /dev/sdb1 > /sys/fs/bcache/register
echo 5fd1b675-ea67-4039-82f6-caa325d10559 > /sys/block/bcache0/bcache/attach
echo 0 > /sys/block/bcache0/bcache/sequential_cutoff
echo 0 > /sys/fs/bcache/5fd1b675-ea67-4039-82f6-caa325d10559/congested_read_threshold_us
echo 0 > /sys/fs/bcache/5fd1b675-ea67-4039-82f6-caa325d10559/congested_write_threshold_us
echo 0 > /sys/fs/bcache/5fd1b675-ea67-4039-82f6-caa325d10559/synchronous
echo writeback > /sys/block/bcache0/bcache/cache_mode
echo 0 > /sys/block/bcache0/bcache/writeback_running
echo 0 > /sys/block/bcache0/bcache/writeback_metadata
in other words for I am trying to get some benchmarking numbers by
using ssd only ie not use hdd for anything. by doing the above I
expected hdd will never be used and all reads and writes will happen
to and from the ssd...
How ever to my shock random writes started happening to the HDD
even iostat confirmed it
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 0.40 16.05 0.00 83.55
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 236.30 0.00 945.20 0 9452
sdb 0.00 0.00 0.00 0 0
bcache0 236.30 0.00 945.20 0 9452
avg-cpu: %user %nice %system %iowait %steal %idle
0.02 0.00 0.42 16.08 0.00 83.48
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 226.90 0.00 908.00 0 9080
sdb 0.00 0.00 0.00 0 0
bcache0 226.50 0.00 906.00 0 9060
avg-cpu: %user %nice %system %iowait %steal %idle
0.02 0.00 0.37 16.08 0.00 83.53
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 235.40 0.00 941.60 0 9416
sdb 0.00 0.00 0.00 0 0
bcache0 235.40 0.00 941.60 0 9416
avg-cpu: %user %nice %system %iowait %steal %idle
0.02 0.00 0.32 16.06 0.00 83.61
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 238.50 0.00 954.00 0 9540
sdb 0.00 0.00 0.00 0 0
bcache0 238.50 0.00 954.00 0 9540
This looks like a possible bug to me. Could you please confirm ?
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