One of my clients had started getting some performance alerts in their monitoring systems: "IO is too high".
This is probably not an error you'd want to have.
In a quick analysis we found out that the alerts and the high IO originated from servers that were installed in a new data center. While the actual CPU utilization devoted to IO wait at the old data center was around 25 percent, in the new data center it was about 75 percent.
Who is to blame?
In the new data center, NetApp 2240c was chosen as a storage appliance, while in the old one IBM V7700 unified was used. Both systems had SAS disks so we didn't expected a major difference between the two. Yet, it was something worth exploring.
In order to verify the source, we made a read/write performance benchmark to both systems by running the following commands:
- Write: dd if=/dev/zero of=/tmp/outfile count=512 bs=1024k
- Read: dd if=/tmp/outfile of=/dev/null bs=4096k
On the NetApp 2240, we got a 0.62GB/s write rate and a 2.0GB/s read rate.
On the IBM V7700 unified, we got 1.1GB/s write rate and 3.4GB/s read rate.
That is almost a 100 percent boost when we used the IBM system!
When selecting and migrating between storage appliances, pay attention to their performance. Otherwise, you may tackle these differences in production.