a question here... what happen if all disks are write-mostly and just ssd is write-behind? why? write-behind is an async feature (md only return ok to filesystem if non write-behind disks are sync writen) write-mostly is a read_balance optimization (ony read from that device if all non-write-mostly devices fail) making all disks write-mostly could allow us to use write-behind on slowest(s) disk(s) another idea... could we change raid1 write code? how? if a total of X write are done, return ok to filesystem, all other devices are marked as write-behind (automatic write-behind) after sync writes disks are marked as non-write-behind again maybe a optimization is: what disk MUST be sync(only non write-behind), what disk MUST BE async (only write-behind), what disk can be async/sync (any write-behind type) another question... can read balance use write-mostly device in a very busy system without failed devices (all mirrors are in sync)? 2011/2/16 Andras Korn <korn@xxxxxxxxxxxxxxxxxxxxxxx>: > On Tue, Feb 15, 2011 at 06:10:17AM -0300, Roberto Spadim wrote: > >> andras could you make some benchmarks to raid1 with round robin read balance? >> at this site: >> www.spadim.com.br/raid1/ > > For the record: we did some benchmarks and while the patch shows promise and > seems to cause no problems, it resulted in no measurable performance > increase for a RAID1 array composed of an SSD and two 7200rpm HDDs. > > Andras > > -- > Andras Korn <korn at elan.rulez.org> > If it ain't broken, play with it until it is. > -- > 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 > -- Roberto Spadim Spadim Technology / SPAEmpresarial -- 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
