iSCSI sequential write

In Figure 1 a sequential-write FIO workload is running against a file system using iSCSI connected devices. The workload is scaled from 1 to 128 jobs running on the KVM guest. The V7000 storage devices are directly attached to the KVM host system via iSCSI.

iSCSI throughput peaks at 8 jobs. Throughput substantially decreases from 32 to 128 jobs. I/O service time data collected during the measurement runs show a doubling from 16 and 32 jobs and continue to substantially increase through 128 jobs. This behavior appears to be contributed to by exceeding the capability of the V7000 configuration used for these measurements. The CPU load is relatively related with the throughput, showing some additional management effort with the increasing amount of workload jobs. The amount of throughput per CPU decreases with the higher number of workload jobs.