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PERFORMANCE COMPARISON AMONG dm cache, bcache and EnhanceIO
The fio config and setup information follows:
HDD : 100GB SSD : 20GB Mode : write through / write back Cache block_size : 4KB for bcache, EnhanceIO and 256KB for dm-cache
The other options have been left to their default values.
Note: 1. In case of dm-cache, we used 2 partitions of same SSD with 1GB partition as metadata and 20GB partition as caching device. This has been done so as to ensure a fair comparison as EnhanceIO and bcache do not have a separate metadata device. 2. In order to ensure proper cache warm up, We have turned off sequential bypass in bcache. This does not impact our performance results as they are taken for random workload.
For each test, we first performed a warm up run using the following fio options:
fio --direct=1 --size=90% --filesize=20G --blocksize=4k --ioengine=libaio --rw=rw --rwmixread=100 --rwmixwrite=0 --iodepth=8 ...
Then, we performed our actual run with the following fio options:
fio --direct=1 --size=100% --filesize=20G --blocksize=4k --ioengine=libaio --rw=randrw --rwmixread=90 --rwmixwrite=10 --iodepth=8 --numjobs=4 --random_distribution=zipf:1.2 ...
Iteration Read Latency ms Write Latency ms Read MB/s Write MB/s 1 1.58 16.21 32.86 3.65 2 1.58 16.35 32.7 3.63 3 1.58 16.54 32.56 3.61 4 1.59 16.6 32.48 3.6 5 1.58 16.58 32.57 3.61 Standard deviation 0.004472136 0.1694992625 0.1489295135 0.02 Mean 1.582 16.456 32.634 3.62
Iteration Read Latency ms Write Latency ms Read MB/s Write MB/s 1 0.86 31.04 23.96 2.65 2 0.31 28.01 29.58 3.28 3 0.39 28.67 28.48 3.16 4 0.39 29.15 29.46 3.27 5 0.28 27.94 29.72 3.3 Standard deviation 0.2364952431 1.2638710377 2.4418435658 0.2748999818 Mean 0.446 28.962 28.24 3.132
Iteration Read Latency ms Write Latency ms Read MB/s Write MB/s 1 0.56 31.08 27.03 3 2 0.61 30 30.7 3.4 3 0.57 29.36 30.72 3.41 4 0.6 30.02 29.79 3.3 5 0.93 35.65 25.55 2.83 Standard Deviation 0.1556598856 2.5511017228 2.343239211 0.2599423013 Mean 0.654 31.222 28.758 3.188
Iteration Read Latency ms Write Latency ms Read MB/s Write MB/s 1 0.33 4.69 145.11 16.14 2 0.33 4.64 146.06 16.23 3 0.33 4.62 146.72 16.3 4 0.33 4.65 145.99 16.2 5 0.33 4.72 144.25 16.02 Standard Deviation 0 0.0403732585 0.9588169794 0.1054514106 Mean 0.33 4.664 145.626 16.178
Iteration Read Latency ms Write Latency ms Read MB/s Write MB/s 1 1.02 2.42 94.49 10.5 2 1.69 4.97 53.89 5.98 3 1.11 2.72 86.2 9.56 4 0.53 0.52 208.54 23.16 5 1.6 4.11 59.47 6.61 Standard Deviation 0.4714339827 1.7076797124 62.7877437881 6.9737091996 Mean 1.19 2.948 100.518 11.162
Iteration Read Latency ms Write Latency ms Read MB/s Write MB/s 1 0.95 1.67 108.08 12 2 0.97 1.63 106.77 11.86 3 0.97 1.61 106.99 11.88 4 1 1.5 104.93 11.66 5 0.94 1.67 107.47 11.95 Standard Deviation 0.0230217289 0.0698569968 1.1842381517 0.13 Mean 0.966 1.616 106.848 11.87
Note:The scripts used for these tests can be found at: https://github.com/stec-inc/EnhanceIO/tree/master/performance_test