On Wed, Jun 10, 2015 at 4:00 PM, Neil Brown <neilb@xxxxxxx> wrote: > On Wed, 10 Jun 2015 15:27:07 -0700 > Ming Lin <mlin@xxxxxxxxxx> wrote: > >> Hi NeilBrown, >> >> As you may already see, I run a lot of tests with 10 HDDs for the patchset >> "simplify block layer based on immutable biovecs" >> >> Here is the summary. >> http://minggr.net/pub/20150608/fio_results/summary.log >> >> MD RAID6 read performance is OK. >> But write performance is much lower than HW RAID6. >> >> Is it a known issue? > > It is not unexpected. > There are two likely reasons. > One is that HW RAID cards often have on-board NVRAM which is used as a > write-behind cache. This allows better throughput by hiding latency and more > often gathering full-stripe writes. HW RAID cards may also have accelerators > for the parity calculations, but that is not likely to make a big difference. > What sort of RAID6 controller do you have? PERC H730 Mini -- 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
