On Tue, Feb 01, 2011 at 02:24:01PM -0200, Roberto Spadim wrote: > thinking about this: > > > I don't think you get the striping performance of raid10,f2 with this > > layout. And that is one of the main advantages of raid10,f2 layout. > > Have you tried it out? > > since you have a raid1, you don?t need striping, you can read from any > mirror, the information is the same, raid1 read is as fast as raid0 > read, just write is slower (it must read on each mirror) > the only problem is raid0 part, or you use linear or stripe, i think > raid10 mdadm algorithm use stripe for raid0 part well, raid0 is for reading sequentially, about double as fast as raid1. https://raid.wiki.kernel.org/index.php/Performance best regards keld > 2011/2/1 Keld Jørn Simonsen <keld@xxxxxxxxxx>: > > On Tue, Feb 01, 2011 at 11:01:33AM +0100, David Brown wrote: > >> On 31/01/2011 23:52, Keld Jørn Simonsen wrote: > >> >raid1+0 and Linux MD raid10 are similar, but significantly different > >> >in a number of ways. Linux MD raid10 can run on only 2 drives. > >> >Linux raid10,f2 has almost RAID0 striping performance in sequential read. > >> >You can have an odd number of drives in raid10. > >> >And you can have as many copies as you like in raid10, > >> > > >> > >> You can make raid10,f2 functionality from raid1+0 by using partitions. > >> For example, to get a raid10,f2 equivalent on two drives, partition them > >> into equal halves. Then make md0 a raid1 mirror of sda1 and sdb2, and > >> md1 a raid1 mirror of sdb1 and sda2. Finally, make md2 a raid0 stripe > >> set of md0 and md1. > > > > I don't think you get the striping performance of raid10,f2 with this > > layout. And that is one of the main advantages of raid10,f2 layout. > > Have you tried it out? > > > > As far as I can see the layout of blocks are not alternating between the > > disks. You have one raid1 of sda1 and sdb2, there a file is allocated on > > blocks sequentially on sda1 and then mirrored on sdb2, where it is also > > sequentially allocated. That gives no striping. > > > >> I don't think there is any way you can get the equivalent of raid10,o2 > >> in this way. But then, I am not sure how much use raid10,o2 actually is > >> - are there any usage patterns for which it is faster than raid10,n2 or > >> raid10,f2? > > > > In theory raid10,o2 should have better performance on SSD's because of > > the low latency, and raid10,o2 doing multireading from each drive, which > > raid0,n2 does not. > > > > We lack some evidence from benchmarks, tho. > > > > best regards > > keld > > -- > > 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 -- 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
