We have several machines on Amazon (ec2) of the type c1.xlarge with 8 cpus, running the Amazon AMI.

Details on the machine:

• 7 GB of memory
• 20 EC2 Compute Units (8 virtual cores with 2.5 EC2 Compute Units each)
• 1690 GB of instance storage
• 64-bit platform
• I/O Performance: High
• API name: c1.xlarge

One out of the several machines is showing a high load average, since we have run the last yum upgrade a couple of weeks a go. We did not yet update the other machines, and everything looks normal on them.

The strange thing is that the top command not showing any hint for the cause of the load. CPUs are -

4.8%us, 1.1%sy, 0.0%ni, 94.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st.

Mem is about 1.5GB free.

Any idea what could it be, or where else can we check?

iostat command on the proper machine:

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           8.97    0.03    4.46    0.19    0.14   86.23

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
xvdap1            1.60         0.69        55.38     587620   47254184
xvdfp2            2.64         1.10        61.04     934786   52091056
xvdfp4            0.86         0.19        41.72     163866   35601920
xvdfp1            4.37        36.59        73.89   31220810   63051504
xvdfp3            8.03         7.08        94.63    6045402   80749184

iostat command on problematic machine:

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           9.29    0.04    5.55    0.26    0.11   84.74

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
xvdap1            2.13         3.34        68.85     246244    5077888
xvdfp1            7.60        74.31       104.88    5480362    7734840
xvdfp3           13.22        73.67       125.00    5433386    9218600
xvdfp4            1.11         0.76        65.08      55762    4799248
xvdfp2            4.16         3.31        99.17     243818    7313264

Many thanks for the help.