bcache on cass1 test node

System specs:
Supermicro PDSML-LN2+, Intel Xeon X3220 CPU, 8 GB ATP RAM
500GB Hitachi HDP72505 disk cached with Intel SSDSA2SH032G1GN (X25-E)
Kernel: 3.11.0

bcache setup:

/dev/sda2 from HDD is cached by /dev/sdb (solely)

kernel info from /sys/fs/<UUID>/

root@cass1:/sys/fs/bcache/2a108307-bab9-42dd-b072-10eeb0c13dd8# find . -type f|xargs -n 1 -t cat
cat ./congested_read_threshold_us
2000
cat ./stop
cat: ./stop: Permission denied
cat ./clear_stats
cat: ./clear_stats: Permission denied
cat ./stats_five_minute/cache_hits
0
cat ./stats_five_minute/cache_bypass_misses
0
cat ./stats_five_minute/bypassed
0
cat ./stats_five_minute/cache_readaheads
0
cat ./stats_five_minute/cache_hit_ratio
0
cat ./stats_five_minute/cache_miss_collisions
0
cat ./stats_five_minute/cache_misses
0
cat ./stats_five_minute/cache_bypass_hits
0
cat ./stats_total/cache_hits
1956872
cat ./stats_total/cache_bypass_misses
0
cat ./stats_total/bypassed
11.3G
cat ./stats_total/cache_readaheads
0
cat ./stats_total/cache_hit_ratio
75
cat ./stats_total/cache_miss_collisions
4276
cat ./stats_total/cache_misses
618713
cat ./stats_total/cache_bypass_hits
568461
cat ./synchronous
1
cat ./congested_write_threshold_us
20000
cat ./congested
0
cat ./btree_cache_size
3.7M
cat ./flash_vol_create
cat: ./flash_vol_create: Permission denied
cat ./io_error_halflife
0
cat ./io_error_limit
8
cat ./block_size
512
cat ./unregister
cat: ./unregister: Permission denied
cat ./average_key_size
444k
cat ./root_usage_percent
0
cat ./journal_delay_ms
100
cat ./bucket_size
512k
cat ./stats_day/cache_hits
994402
cat ./stats_day/cache_bypass_misses
0
cat ./stats_day/bypassed
6.8G
cat ./stats_day/cache_readaheads
0
cat ./stats_day/cache_hit_ratio
72
cat ./stats_day/cache_miss_collisions
2680
cat ./stats_day/cache_misses
369715
cat ./stats_day/cache_bypass_hits
405741
cat ./stats_hour/cache_hits
8957
cat ./stats_hour/cache_bypass_misses
0
cat ./stats_hour/bypassed
568M
cat ./stats_hour/cache_readaheads
0
cat ./stats_hour/cache_hit_ratio
25
cat ./stats_hour/cache_miss_collisions
199
cat ./stats_hour/cache_misses
26750
cat ./stats_hour/cache_bypass_hits
62195
cat ./tree_depth
1
cat ./cache_available_percent
61
cat ./internal/btree_split_last_sec
6222
cat ./internal/prune_cache
cat: ./internal/prune_cache: Permission denied
cat ./internal/bset_tree_stats
btree nodes:            16
written sets:           31
unwritten sets:         16
written key bytes:      2044264
unwritten key bytes:    0
floats:                 15935
failed:                 7
cat ./internal/btree_read_max_duration_us
935
cat ./internal/writeback_keys_failed
1211
cat ./internal/copy_gc_enabled
0
cat ./internal/btree_split_average_duration_us
3491
cat ./internal/btree_sort_max_duration_us
911
cat ./internal/btree_nodes
14
cat ./internal/cache_read_races
0
cat ./internal/btree_shrinker_disabled
0
cat ./internal/btree_sort_average_frequency_ms
8358
cat ./internal/btree_gc_average_frequency_sec
1054
cat ./internal/btree_split_max_duration_us
856
cat ./internal/btree_gc_average_duration_ms
157
cat ./internal/try_harder_max_duration_us
0
cat ./internal/try_harder_last_ms
-1
cat ./internal/try_harder_average_duration_us
0
cat ./internal/active_journal_entries
3
cat ./internal/btree_split_average_frequency_sec
16
cat ./internal/btree_gc_last_sec
6424
cat ./internal/writeback_keys_done
864824
cat ./internal/btree_read_average_frequency_ms
4712
cat ./internal/trigger_gc
cat: ./internal/trigger_gc: Permission denied
cat ./internal/btree_read_average_duration_us
5111
cat ./internal/try_harder_average_frequency_ms
0
cat ./internal/btree_sort_last_ms
6196264
cat ./internal/btree_gc_max_duration_ms
2
cat ./internal/btree_read_last_ms
72813466
cat ./internal/btree_cache_max_chain
1
cat ./internal/gc_always_rewrite
0
cat ./internal/btree_sort_average_duration_us
667
cat ./internal/btree_used_percent
45
cat ./dirty_data
11.2G

iozone:
Iozone: Performance Test of File I/O
                Version $Revision: 3.397 $
                Compiled for 64 bit mode.
                Build: linux-AMD64

cmdline: iozone -R -e -s 2g -t 32 -M -r 128k

error
[...]
       Children see throughput for 32 rewriters        =   76320.88 KB/sec
        Parent sees throughput for 32 rewriters         =   76050.53 KB/sec
        Min throughput per process                      =    2359.19 KB/sec
        Max throughput per process                      =    2504.61 KB/sec
        Avg throughput per process                      =    2385.03 KB/sec
        Min xfer                                        = 1997184.00 KB


Error in file: Found ?6d? Expecting ?6d6d6d6d6d6d6d6d? addr 7f2913a08000
Error in file: Position 382894080
Record # 2921 Record size 128 kb
where 7f2913a08000 loop 32768


Error in file: Found ?6d? Expecting ?6d6d6d6d6d6d6d6d? addr 7f2913a01000
Error in file: Position 552865792
Record # 4218 Record size 128 kb
where 7f2913a01000 loop 4096


Error in file: Found ?6d? Expecting ?6d6d6d6d6d6d6d6d? addr 7f2913a12000
Error in file: Position 667623424
Record # 5093 Record size 128 kb
where 7f2913a12000 loop 73728


Error in file: Found ?6d? Expecting ?6d6d6d6d6d6d6d6d? addr 7f2913a17000
Error in file: Position 638021632
Record # 4867 Record size 128 kb
where 7f2913a17000 loop 94208


Error in file: Found ?6d? Expecting ?6d6d6d6d6d6d6d6d? addr 7f2913a1f000
Error in file: Position 628879360
Record # 4797 Record size 128 kb
where 7f2913a1f000 loop 126976


Error in file: Found ?6d? Expecting ?6d6d6d6d6d6d6d6d? addr 7f2913a0f000
Error in file: Position 618983424
Record # 4722 Record size 128 kb
where 7f2913a0f000 loop 61440

        Children see throughput for 32 readers          =   87766.21 KB/sec
        Parent sees throughput for 32 readers           =   87707.06 KB/sec
        Min throughput per process                      =    2768.13 KB/sec
        Max throughput per process                      =    4497.25 KB/sec
        Avg throughput per process                      =    2742.69 KB/sec
        Min xfer                                        = 1291904.00 KB
[...]