Yes you are. If you loose any one of your disks with a raid 0 spanning all drive you will loose all the data in that directory.
And disks do die. Yes you get better single threaded performance but are putting that entire directory/data set at higher risk Cheers On Saturday, July 30, 2016, Shady Xu <[email protected]> wrote: > Hi, > > It's widely known that we should mount disks to different directory > without any RAID configurations because it provides the best io performance. > > However, lately I have done some tests with three different configurations > and found this may not be the truth. Below are the configurations and > statistics shown by command 'iostat -x'. > > Configuration A: RAID 0 all 12 disks to one directory > Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz > avgqu-sz await r_await w_await svctm %util > sdb 0.01 0.59 112.02 65.92 15040.07 15856.86 347.27 > 0.32 1.81 2.36 0.86 0.93 16.49 > > > ------------------------------------------------------------------------------ > > Configuration B: No RAID at all > Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz > avgqu-sz await r_await w_await svctm %util > sdc 0.01 0.12 2.88 5.23 364.54 1247.10 397.52 > 0.76 93.80 9.05 140.42 2.44 1.98 > sdg 0.01 0.07 2.39 5.27 328.72 1246.51 410.93 > 0.75 97.88 10.93 137.33 2.63 2.02 > sdl 0.01 0.07 2.59 5.46 340.61 1299.00 407.00 > 0.82 102.18 9.64 146.09 2.55 2.05 > sdf 0.01 0.11 2.28 5.02 291.48 1197.00 407.99 > 0.72 99.23 9.15 140.12 2.62 1.91 > sdb 0.01 0.07 2.69 5.23 334.19 1238.20 396.99 > 0.74 93.84 8.10 137.98 2.41 1.91 > sde 0.01 0.11 2.81 5.27 376.54 1262.25 405.56 > 0.79 97.62 10.96 143.84 2.58 2.08 > sdk 0.01 0.12 3.02 5.20 371.92 1244.48 392.93 > 0.79 96.07 8.63 146.85 2.48 2.04 > sda 0.00 0.07 2.82 5.33 370.06 1260.68 400.52 > 0.78 96.09 9.72 141.74 2.49 2.03 > sdi 0.01 0.11 3.09 5.30 378.19 1269.98 392.63 > 0.78 92.47 5.98 142.88 2.31 1.94 > sdj 0.01 0.07 3.04 5.02 365.32 1185.24 385.01 > 0.74 92.22 6.31 144.29 2.40 1.93 > sdh 0.01 0.07 2.74 5.34 356.22 1264.28 401.06 > 0.78 96.81 11.36 140.75 2.55 2.06 > sdd 0.01 0.11 2.47 5.39 343.22 1292.23 416.20 > 0.76 96.48 10.26 135.96 2.54 1.99 > > > ------------------------------------------------------------------------------ > > Configuration C: RAID 0 each 12 disks to 12 different directories > Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz > avgqu-sz await r_await w_await svctm %util > sdd 0.00 0.10 8.88 7.42 1067.65 1761.12 346.94 > 0.13 7.94 3.64 13.09 0.46 0.75 > sdb 0.00 0.09 8.83 7.52 1066.16 1784.79 348.65 > 0.13 8.02 3.75 13.02 0.47 0.76 > sdc 0.00 0.10 8.82 7.48 1073.74 1776.02 349.61 > 0.13 8.09 3.76 13.19 0.47 0.76 > sde 0.00 0.10 8.74 7.46 1060.79 1771.46 349.63 > 0.13 7.80 3.53 12.81 0.45 0.73 > sdg 0.00 0.10 8.93 7.46 1101.14 1772.73 350.64 > 0.13 7.81 3.70 12.71 0.47 0.77 > sdf 0.00 0.09 8.75 7.46 1062.06 1772.08 349.73 > 0.13 8.03 3.78 13.00 0.46 0.75 > sdh 0.00 0.10 9.09 7.45 1114.94 1770.07 348.76 > 0.13 7.83 3.69 12.89 0.47 0.77 > sdi 0.00 0.10 8.91 7.43 1086.85 1761.30 348.48 > 0.13 7.93 3.64 13.07 0.46 0.75 > sdj 0.00 0.10 9.04 7.46 1111.32 1768.79 349.15 > 0.13 7.79 3.64 12.82 0.46 0.76 > sdk 0.00 0.10 9.12 7.51 1122.00 1783.41 349.49 > 0.13 7.82 3.72 12.80 0.48 0.79 > sdl 0.00 0.10 8.91 7.49 1087.98 1777.77 349.49 > 0.13 7.89 3.69 12.89 0.46 0.75 > sdm 0.00 0.09 8.97 7.52 1098.82 1787.10 349.95 > 0.13 7.96 3.79 12.94 0.47 0.78 > > It seems the raid 0 all disks to one directory configuration is the one > which provides the best disk performance and the no raid configuration > provides the worst performance. That's a total opposite fact comparing to > the widely known one. Am I doing anything wrong? >
