On Mon, 2 Jun 2008, ???? ????????? wrote:
Hello. I have a simple question. I just created mdadm raid10 with four disks. The raid build process complete successfully. All of 4 HDD are connected with separate SATA wires directly to motherboard.
The mode of operation (selected in bios) neither AHCI nor RAID. I decide to acheive performance information of software RAID. So I read 10 blocks by 64Mb. This give me roughly performance of one disk. (I expect that it will be 4x speed ! it should read from 4 hdd simultaneously!!!, BUT NOT! )
1. What motherboard? Does it have PCI-e lanes? Or is the I/O on the regular PCI bus? If you have 8 CPUs as it shows below you really should not be running into I/O problems, see my earlier post to the mailing list, you want to run something similar to: dd if=/dev/sda of=/dev/null bs=1M dd if=/dev/sdb of=/dev/null bs=1M Then, run: dstat -D sda,sdb,sdc,sdd Show the output!
So, second test were reading 10 blocks (from 0 to 9) in one process, and 10 blocks (from 10 to 19) in second thread. I acheive performance of half disk... in each thread.
2. I am not sure how RAID10 in linux handles it but with raid1 you need to use 2 or 3 threads simultaenously to pull data from multiple disks _and_ you need a backplane/interface/chipset that can handle that bandwidth. Justin. -- 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
