Per Jessen wrote:
Sandy Drobic wrote:
Per Jessen wrote:
Greg Freemyer wrote:
Since 1MB was faster than 1GB for some reason, I would try the 4k one just out of curiosity, but you're likely right it is far slower.
It wasn't that bad - using bs=4k, the file copy was done in 31minutes at 11.5Mb/sec (dd's transfer-rate). That's still pretty miserable compared to the power of the other server components. A cheap sata raid5 on a 3ware controller is already a step up.
This is a raid5 with 5 sata disks (system with 8 GB RAM):
dd if=/dev/zero of=/tmp/testfile bs=1024k count=20480 20480+0 records in 20480+0 records out 21474836480 bytes (21 GB) copied, 262.764 s, 81.7 MB/s
Yep, very impressive. To be honest, I had also expected more throughput on my system (RAID1 on 2 SATA drives). In pure write speed I get 29Mb/s - your 3ware controller must be helping a lot here. Interestingly, I got 33Mb/s on an older PC with a plain PATA drive ... I guess RAID1 does have its price.
All my raid controllers come with a bbu so I can use the fast write-back mode instead of the slower write-through. Also, don't forget that I am using five disks here, so IO is distributed much better than on raid1.
dd if=/tmp/testfile of=/dev/null bs=1024k 20480+0 records in 20480+0 records out 21474836480 bytes (21 GB) copied, 71.9161 s, 299 MB/s
How did you manage that? 300Mb/s read speed??? I tried the same and got 47Mb/s. Is that the 3ware controller again?
Of course, the read speed on raid5 is very fast, and the controller has its own cache on board. If the controller uses a multiline PCI-e slot he's got enough bandwidth to use the full disk speed. Theoretically, I should be able to get close to 400 mb/s, since the single disks can offer about 100 mb/s. I've have another server with the same controller/disks here, though configured as raid 10 with 8 disks(4 x raid1). Write speed with bonnie was about 120 mb/s. I would have expected a lot more, it seems the striping even with raid 10 is a limiting factor with that controller. Read speed on that system is close to 400 mb/s, which I expected. Hopefully I can reconfigure the server in a few month (it's only supposed to be a temp server). Then I can check if raid5 with 8 disks is really that much worse than raid 10. I begin to suspect that I will get at least the same write performance on a raid5 with that number of disks as on raid10.
dd if=/tmp/testfile of=/tmp/testfile2 bs=1024k 20480+0 records in 20480+0 records out 21474836480 bytes (21 GB) copied, 636.322 s, 33.7 MB/s
The sad fact is that hdd speed, especially access time has not evolved with the same speed as other parts of pc hardware.
The operator bus, the memory bus and the peripheral ditto are also way behind the CPU, but that is the way it has always been.
Not really, for a long time the parallel bus of the scsi system was a limiting factor, also the pci bus system. With pci-e you can use a lot more bandwidth. -- Sandy List replies only please! Please address PMs to: news-reply2 (@) japantest (.) homelinux (.) com -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org