On 12/16/2013 7:13 AM, lilofile wrote: > mpt2sas 6Gb/s, PCIE 2.0，the card is four port,so theoretical ratio can reach to 2.4Gb/s,it is not bottleneck. I test read two raid5 using dd, > such as dd if=/dev/md0 of=/dev/zero 1M > dd if=/dev/md1 of=/dev/zero 1M > the total read bandwidth can reach to 2.3GB/s,so I/O bus is not a problem. Why are you using dd again? I explained to you in your previous thread why dd will never saturate your SSDs with write IO. Use FIO. If you don't know how to make FIO do what you want then ask. BTW, don't start a new thread for the same issue. Your last thread and this thread deal with the same RAID5 on STEC SSDs issue. By starting a new thread everyone loses context and history, which are critically important when keeping track of performance tests and configurations. I can't help but point out some irony here. You're concerned with throughput, yet you're connecting 12 SSDs, ~500 MB/s each, to an SAS backplane which connects via 4-lane 6G SAS to the HBA. With RAID5 that's 5 GB/s SAS hardware throughput funneled through a 2.4 GB/s SFF-8088 cable. So once you test properly, and see the write throughput you already have, you'll see you're limited to half the hardware throughput by your cabling/backplane. For reads you already are seeing this limit. -- Stan -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
