On Thu, Apr 2, 2009 at 7:16 PM, Vladislav Bolkhovitin <vst@xxxxxxxx> wrote: > Bart Van Assche, on 04/02/2009 12:14 AM wrote: >> I have repeated some of these performance tests for iSCSI over IPoIB >> (two DDR PCIe 1.0 ConnectX HCA's connected back to back). The results >> for the buffered I/O test with a block size of 512K (initiator) >> against a file of 1GB residing on a tmpfs filesystem on the target are >> as follows: >> >> write-test: iSCSI-SCST 243 MB/s; IET 192 MB/s. >> read-test: iSCSI-SCST 291 MB/s; IET 223 MB/s. >> >> And for a block size of 4 KB: >> >> write-test: iSCSI-SCST 43 MB/s; IET 42 MB/s. >> read-test: iSCSI-SCST 288 MB/s; IET 221 MB/s. > > Do you have any thoughts why writes are so bad? It shouldn't be so.. By this time I have run the following variation of the 4 KB write test: * Target: iSCSI-SCST was exporting a 1 GB file residing on a tmpfs filesystem. * Initiator: two processes were writing 4 KB blocks as follows: dd if=/dev/zero of=/dev/sdb bs=4K seek=0 count=131072 oflag=sync & dd if=/dev/zero of=/dev/sdb bs=4K seek=131072 count=131072 oflag=sync & Results: * Each dd process on the initiator was writing at a speed of 37.8 MB/s, or a combined writing speed of 75.6 MB/s. * CPU load on the initiator system during the test: 2.0. * According to /proc/interrupts, about 38000 mlx4-comp-0 interrupts were triggered per second. These results confirm that the initiator system was the bottleneck during the 4 KB write test, not the target system. Bart. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
