Mindaugas Riauba wrote: >>> By the way did you try to test random read performance and latency >>> of XIV? Looking into architecture (multiple hosts with 7200rpm SATA >>> drives interconnected via 1Gb Ethernet) it should not perform well in >>> this area. >> >> Yes: When I test with fio (6 parallel tasks, aio, direct I/O, depth >> 256, 70% reads), the XIV beats the local RAID by a _wide_ margin. > > Could you try 1 task, 100% random read? And give us results? :)
Yes, but I'm not sure which utility to use to create 100% random reads. Perhaps fio in a 100% read mode? >> I know that the XIV's focus is on parallel I/O, but still: I'm >> wondering _where_ in the system the bottleneck appears (knowing that I >> can get fine throughput if I run (e.g.) six dd/cat processes in >> parallel). > > XIV is the bottleneck. As I already wrote - SAN storage boxes are > tuned so that they will not give their full power to 1 I/O process. But XIV can't see processes on the Linux box. So I reckon it's the operating system's duty to spread the I/O over the available paths, as long as there aren't other factors (such as CPU bottlenecks) standing in the way? This, of course, assumes an active-active(-active)*-situation. > But you can look into alignment issues. If I remember right XIV > splits data into 1MB chunks but I don't know what block size is used at > lower level. True, its chunks are 1MB. But what would I align? Setting ext3's block size to 1MB seems like a rather weird idea. > Also you can try to tune read-ahead settings on XIV if that > is possible. I don't think that's possible, but I tried it on the OS side (blockdev -- setra ...) without seeing any change. -- Regards, Troels Arvin <[email protected]> http://troels.arvin.dk/ _______________________________________________ rhelv5-list mailing list [email protected] https://www.redhat.com/mailman/listinfo/rhelv5-list
