磁盘io问题排查

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
top - 08:45:04 up 722 days, 17:33,  1 user,  load average: 3.28, 3.12, 3.09
Tasks: 143 total,   1 running, 142 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.0 us,  0.0 sy,  0.0 ni, 64.1 id, 35.8 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem : 65807536 total,   370956 free, 37718456 used, 27718124 buff/cache
KiB Swap:  4194300 total,  4194300 free,        0 used. 24181116 avail Mem

[root@dbslave-010007081120 relaylog]# iostat -x 1 5
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.00    0.00    0.13   24.91    0.00   74.97

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
vda               0.00     8.00    0.00    2.00     0.00    40.00    40.00     0.00    0.50    0.00    0.50   0.50   0.10
vdb               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
vdc               0.00     0.00    0.00    2.00     0.00   904.00   904.00     4.90  994.00    0.00  994.00 492.00  98.40