I see. Well, whether MD is smart enough to rearrange a queue when the arrays are sharing disks or not, it still means that you can't run your processes in parallel. I did see MD put the arrays in queue during resyncs when I had a similar setup. I didn't benchmark the arrays at that time, so I don't have solid numbers of how much of a performance penalty that setup caused. On Wed, Oct 14, 2009 at 9:23 AM, Antonio Perez <ap23563m@xxxxxxx> wrote: > Majed B. wrote: > >> I think I already answered your question: >> >>> For desktop usage it's OK to use that setup since you won't be writing >>> to / and the other segments a lot at the same time. >> >>> If you're running an application which writes a lot of data to / and >>> you require to read/write a lot of data of the rest of the disk, it >>> will conflict and slow things down a lot. >>> >>> Basically, you're partitioning each disk and making each partition >>> belong to an array. >> >> If you misunderstood part, or I did, let me know :) > > Thanks Majeb. I believe I understand you. > > This is what I get from your comment: > > If the disks are setup with several partitions, and the corresponding > partitions belong to a md array as this: > sd[a..d]1 --> md1 > sd[a..d]2 --> md2 > sd[a..d]3 --> md3 > > If md1 is used as / and md2 is used as /home (or /data) there will be no > concurrent reads to both places. > > While this may be true, depending on the specific application, it is not > what I am asking. > ________________________________________________________________________ > > The point is: > > If md1 is used as /data1 and md2 is used as /data2 will it work? > > Will the md system be aware that those are on the same disk (spindle) and > use the correct queuing on the reads for the best reading speed possible? > > Or will md get confused on the correct read sequence causing additional head > seeks which will degrade overall performance. > > Sorry if I confuse you more, this is not an "simple" question. > > Please read Robin Hill answer. :-) > > -- > Antonio Perez > > -- > 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 > -- Majed B. -- 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
