On Sun, Feb 15, 2004 at 01:54:11AM -0800, Matt Thrailkill wrote: > The you don't get as good performance because hdc1 is slow enough to > really drag it down. Think about it, if reads are all going about > sequentially, it has to spend alot of time waiting on that 16mb/s drive > compared to the others. I would have thought the disks would have worked towards gaining performance enhancements in some cumulative way, is that not so, in theory? So why is 3 disks slower than 2? > You probably can't get 100mb/s with the two because that would be pretty > efficient, and there's probably more overhead than that. > > Shouldn't the 80gb drive be going faster than 16mb/s though? Have you > checked hdparm to make sure dma and all the goodies are turned on for > it? I have a 40 GB segate disk also, on the same motherboard IDE controller, it runs about 40 MB/s. So yes, the hdc1 should go faster, and I have measured something like 40 MB/s on it in idler times. I think it is because it is running other processes. The machine is a ftp mirror and the disk has RedHat and Fedora ISO images, so it is quite popular. > On Sun, 2004-02-15 at 02:04, Keld Jørn Simonsen wrote: > > Hi > > > > I have some strange performance results on a raid0 > > I have 4 IDE disks on two controllers, the one on the > > motherboard of the duron 1 GHz mackine, the other a promise TX2 plus > > SATA + PATA controller. I run kernel 2.4.22 > > > > The disks and hdparm -t on each of them > > > > /dev/hdc1 seagate 80 GB 16 MB/s > > /dev/sda1 maxtor sata 200 GB 50 MB/s > > /dev/sdb7 maxtor 160 GB 54 MB/s > > > > The partitions are al about 5 GB each. > > > > If I make a raid0 device of all of them I get a thruput of 45 MB/s > > IIf I exclude the hdc1 partition, I get around 75 MB/s. > > The system is a little loaded - but that would be normal operating > > conditions. CPU is 90 % idle. I have about 100 MB free RAM. > > > > Why is it slower with 3 disks in the raid0 than > > 2 disks? Why don't I get approx 100 MB/s out of just the two? > > > > Best regards > > Keld - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
