With the SE700, FC channels operating at 8 Gbit/s are available for the first time on /390 servers. The measurements below are designed to show what throughputs can be achieved over these channels. All measurements are based on a cache hit rate of 100%. The throughputs for random and sequential access are consequently identical in terms of measurement variance.
The series of measurements for two particularly frequent cases are shown below:
IOs/s with 4KB blocks (rounded to 100 IOs/s) and
Mbyte/s when using 480-KB blocks.
Channels | PAV | Vol. | Tasks | Read | Write | Random25 | |||
IO/s | Mbyte/s | IO/s | Mbyte/s | IO/s | Mbyte/s | ||||
1 | No | 1 | 1 | 5,000 | 210 | 3,900 | 181 | 4,600 | 201 |
6 | 6 | 23,700 | 577 | 19,700 | 599 | 22,600 | 687 | ||
6 | 12 | 24,300 | 579 | 20,400 | 604 | 23,300 | 700 | ||
6 | 18 | 24,300 | 581 | 20,200 | 608 | 23,300 | 702 | ||
1 | Yes, 3 | 1 | 1 | 5,000 | 210 | 3,800 | 181 | 4,600 | 201 |
6 | 6 | 23,700 | 577 | 19,700 | 599 | 22,600 | 686 | ||
6 | 12 | 27,100 | 584 | 26,200 | 603 | 26,700 | 766 | ||
6 | 18 | 28,000 | 585 | 27,800 | 604 | 27,800 | 769 | ||
The results show that a single task cannot fully utilize the channel. In the case of parallel loads, up to 28,000 IOs/s are achieved with small blocks. The maximum throughput in one direction (read, write) is approx. 600 Mbyte/s when large blocks are used. However, the throughput of each individual task in the case of this high workload is considerably lower.
In the event of simultaneous reading and writing (Random25), no higher IO rates can be achieved, but considerably higher throughput can. If the ratio of write to read IOs is 1:1, over 1,000 Mbyte/s is possible.
The tables below show the IO rates and throughputs for various block sizes, taking the measurements with 6 tasks and PAV as an example.
Load type | IO rate in IOs/s (6 tasks, 1 channel) with block size | ||||||
2 KB | 4 KB | 8 KB | 16 KB | 32 KB | 160 KB | 480 KB | |
Sequential read | 24,000 | 23,700 | 23,000 | 21,200 | 17,600 | 3,700 | 1,200 |
Sequential write | 20,000 | 19,700 | 19,000 | 17,000 | 13,600 | 3,700 | 1,200 |
Random25 | 22,900 | 22,600 | 21,700 | 19,700 | 16,100 | 4,200 | 1,500 |
Load type | Throughput in Mbyte/s (6 tasks, 1 channel) with block size | ||||||
2 KB | 4 KB | 8 KB | 16 KB | 32 KB | 160 KB | 480 KB | |
Sequential reads | 46 | 92 | 179 | 330 | 550 | 580 | 577 |
Sequential write | 39 | 77 | 148 | 265 | 426 | 581 | 599 |
Random25 | 44 | 88 | 169 | 308 | 502 | 663 | 686 |