i think it's cpu wait i/o 2011/1/31 Keld Jørn Simonsen <keld@xxxxxxxxxx>: > On Mon, Jan 31, 2011 at 09:37:46AM +0000, Mathias Burén wrote: >> On 31 January 2011 08:52, Keld Jørn Simonsen <keld@xxxxxxxxxx> wrote: >> > If your intallation is CPU bound, and you are >> > using an Atom N270 processor or the like, well some ideas: >> > >> > The Atom CPU may have threading, so you could run 2 RAIDs >> > which then probably would run in each thread. >> > It would cost you 1 more disk if you run 2 RAID5's >> > so you get 8 TB payload out of your 12 GB total (6 drives of 2 TB each). >> > >> > Another way to get better performance could be to use less >> > CPU-intensitive RAID types. RAID5 is intensitive as it needs to >> > calculate XOR information all the time. Maybe a mirrored >> > raid type like RAID10,f2 would give you less CPU usage, >> > and the run 2 RAIDS to have it running in both hyperthreads. >> > Here you would then only get 6 TB payload of your 12 GB disks, >> > but then also probably a faster system. >> > >> > Best regards >> > keld >> > >> >> Hi, >> >> It's interesting what you say about the XOR calculations. I thought >> that it was only calculated on writes? The Atom (330) has HT, so Linux >> sees 4 logical CPUs. > > Yes you are right, it only calculates XOR on writes with RAID5. > But then I am puzzled what all these CPU cycles are used for. > Also many cycles are used on mirrored raid types. Why? > Maybe some is because of LVM? I have been puzzled for a long time why > ordinary RAID without LVM need to use so much CPU. Maybe a lot of data > sguffling between buffers? Neil? > > 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
