restbase1007 reported errors on sdb, trying to confirm I'm running stress --hdd 100 --hdd-bytes 100M on /var/tmp (raid0) and sdb shows constantly-higher latencies than sda:
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 2.99 96.08 0.00 0.93
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 0.00 0.00 0.00 210.00 0.00 106664.00 1015.85 82.78 380.72 0.00 380.72 4.76 100.00
sda 0.00 78.00 3.00 161.00 12.00 76140.00 928.68 41.11 139.59 76.00 140.77 3.07 50.40
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 1.62 98.38 0.00 0.00
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 0.00 1.00 0.00 255.00 0.00 130560.00 1024.00 138.72 527.89 0.00 527.89 3.92 100.00
sda 0.00 0.00 5.00 314.00 20.00 160768.00 1008.08 42.56 186.90 16.80 189.61 2.86 91.20
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 1.35 98.65 0.00 0.00
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 0.00 0.00 0.00 223.00 0.00 114176.00 1024.00 139.05 587.68 0.00 587.68 4.48 100.00
sda 0.00 0.00 2.00 240.00 8.00 122880.00 1015.60 20.58 89.90 18.00 90.50 3.34 80.80
avg-cpu: %user %nice %system %iowait %steal %idle
0.07 0.00 1.28 98.66 0.00 0.00
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 0.00 0.00 0.00 224.00 0.00 114688.00 1024.00 140.65 589.96 0.00 589.96 4.46 100.00
sda 0.00 0.00 3.00 238.00 12.00 121856.00 1011.35 21.48 89.15 0.00 90.27 3.07 74.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 1.47 98.53 0.00 0.00
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 0.00 1.00 0.00 255.00 0.00 130560.00 1024.00 136.62 558.04 0.00 558.04 3.92 100.00
sda 0.00 0.00 8.00 229.00 32.00 117248.00 989.70 24.83 94.97 34.50 97.08 4.05 96.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.07 0.00 2.67 97.26 0.00 0.00
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 0.00 41.00 0.00 295.00 0.00 149680.00 1014.78 63.05 359.63 0.00 359.63 3.39 100.00
sda 0.00 0.00 8.00 215.00 32.00 110080.00 987.55 20.75 98.78 60.50 100.20 2.85 63.60