nate wrote: > Chan Chung Hang Christopher wrote: > >> Complete bollocks. The bottleneck is not the drives themselves as >> whether it is SATA/PATA disk drive performance has not changed much >> which is why 15k RPM disks are still king. The bottleneck is the bus be >> it PCI-X or PCIe 16x/8x/4x or at least the latencies involved due to bus >> traffic. >> > > In most cases the bottleneck is the drives themselves, there is > only so many I/O requests per second a drive can handle. Most workloads > are random, rather than sequential, so the amount of data you can > pull from a particular drive can be very low depending on what > your workload is. > Which is true whether you are running hardware or software raid 0/1/1+0. However, when it comes to software raid, given enough disks, the bottleneck moves from the disk to the bus especially for raid5/6. > > Fortunately the large caches(12GB per controller, mirrored with > another controller) on the array buffer the higher response > times on the disks resulting in host response times of > around 20 milliseconds for reads, and 0-5 milliseconds for > writes, which by most measures is excellent. > > Haha, yeah, if you have such large scale setups, nobody would compare software raid.