On Mon, Jan 31, 2011 at 12:43:56PM -0200, Roberto Spadim wrote: > i think it's cpu wait i/o Well, you better be sure. Please have a closer look. Normally saying that a process is CPU bound means that it is not IO bound. Best regards keld > 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
