Hi All, Here are some final results of testing with the reference implementation for compressing blocks and transactions. This implementation also concatenates blocks and transactions when possible so you'll see data sizes in the 1-2MB ranges. Results below show the time it takes to sync the first part of the blockchain, comparing Zlib to the LZOx library. (LZOf was also tried but wasn't found to be as good as LZOx). The following shows tests run with and without latency. With latency on the network, all compression libraries performed much better than without compression. I don't think it's entirely obvious which is better, Zlib or LZO. Although I prefer the higher compression of Zlib, overall I would have to give the edge to LZO. With LZO we have the fastest most scalable option when at the lowest compression setting which will be a boost in performance for users that want peformance over compression, and then at the high end LZO provides decent compression which approaches Zlib, (although at a higher cost) but good for those that want to save more bandwidth. Uncompressed 60ms Zlib-1 (60ms) Zlib-6 (60ms) LZOx-1 (60ms) LZOx-999 (60ms) 219 299 296 294 291 432 568 565 558 548 652 835 836 819 811 866 1106 1107 1081 1071 1082 1372 1381 1341 1333 1309 1644 1654 1605 1600 1535 1917 1936 1873 1875 1762 2191 2210 2141 2141 1992 2463 2486 2411 2411 2257 2748 2780 2694 2697 2627 3034 3076 2970 2983 3226 3416 3397 3266 3302 4010 3983 3773 3625 3703 4914 4503 4292 4127 4287 5806 4928 4719 4529 4821 6674 5249 5164 4840 5314 7563 5603 5669 5289 6002 8477 6054 6268 5858 6638 9843 7085 7278 6868 7679 11338 8215 8433 8044 8795 These results from testing on a highspeed wireless LAN (very small latency) Results in seconds Num blocks sync'd Uncompressed Zlib-1 Zlib-6 LZOx-1 LZOx-999 10000 255 232 233 231 257 20000 464 414 420 407 453 30000 677 594 611 585 650 40000 887 782 795 760 849 50000 1099 961 977 933 1048 60000 1310 1145 1167 1110 1259 70000 1512 1330 1362 1291 1470 80000 1714 1519 1552 1469 1679 90000 1917 1707 1747 1650 1882 100000 2122 1905 1950 1843 2111 110000 2333 2107 2151 2038 2329 120000 2560 2333 2376 2256 2580 130000 2835 2656 2679 2558 2921 140000 3274 3259 3161 3051 3466 150000 3662 3793 3547 3440 3919 160000 4040 4172 3937 3767 4416 170000 4425 4625 4379 4215 4958 180000 4860 5149 4895 4781 5560 190000 5855 6160 5898 5805 6557 200000 7004 7234 7051 6983 7770 The following show the compression ratio acheived for various sizes of data. Zlib is the clear winner for compressibility, with LZOx-999 coming close but at a cost. range Zlib-1 cmp% Zlib-6 cmp% LZOx-1 cmp% LZOx-999 cmp% 0-250b 12.44 12.86 10.79 14.34 250-500b 19.33 12.97 10.34 11.11 600-700 16.72 n/a 12.91 17.25 700-800 6.37 7.65 4.83 8.07 900-1KB 6.54 6.95 5.64 7.9 1KB-10KB 25.08 25.65 21.21 22.65 10KB-100KB 19.77 21.57 14.37 19.02 100KB-200KB 21.49 23.56 15.37 21.55 200KB-300KB 23.66 24.18 16.91 22.76 300KB-400KB 23.4 23.7 16.5 21.38 400KB-500KB 24.6 24.85 17.56 22.43 500KB-600KB 25.51 26.55 18.51 23.4 600KB-700KB 27.25 28.41 19.91 25.46 700KB-800KB 27.58 29.18 20.26 27.17 800KB-900KB 27 29.11 20 27.4 900KB-1MB 28.19 29.38 21.15 26.43 1MB -2MB 27.41 29.46 21.33 27.73 The following shows the time in seconds to compress data of various sizes. LZO1x is the fastest and as file sizes increase, LZO1x time hardly increases at all. It's interesing to note as compression ratios increase LZOx-999 performs much worse than Zlib. So LZO is faster on the low end and slower (5 to 6 times slower) on the high end. range Zlib-1 Zlib-6 LZOx-1 LZOx-999 cmp% 0-250b 0.001 0 0 0 250-500b 0 0 0 0.001 500-1KB 0 0 0 0.001 1KB-10KB 0.001 0.001 0 0.002 10KB-100KB 0.004 0.006 0.001 0.017 100KB-200KB 0.012 0.017 0.002 0.054 200KB-300KB 0.018 0.024 0.003 0.087 300KB-400KB 0.022 0.03 0.003 0.121 400KB-500KB 0.027 0.037 0.004 0.151 500KB-600KB 0.031 0.044 0.004 0.184 600KB-700KB 0.035 0.051 0.006 0.211 700KB-800KB 0.039 0.057 0.006 0.243 800KB-900KB 0.045 0.064 0.006 0.27 900KB-1MB 0.049 0.072 0.006 0.307