From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roberto Spadim Subject: Re: Performance question, RAID5 Date: Mon, 31 Jan 2011 12:43:56 -0200 Message-ID: References: <20110130094444.68288b0e@natsu> <20110130171533.4c9e236b@natsu> <4D45C3FA.2040900@hardwarefreak.com> <20110131085202.GA25912@www2.open-std.org> <20110131131131.GA26525@www2.open-std.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20110131131131.GA26525@www2.open-std.org> Sender: linux-raid-owner@vger.kernel.org To: =?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= Cc: =?ISO-8859-1?Q?Mathias_Bur=E9n?= , Stan Hoeppner , Roman Mamedov , CoolCold , Linux-RAID List-Id: linux-raid.ids i think it's cpu wait i/o 2011/1/31 Keld J=F8rn Simonsen : > On Mon, Jan 31, 2011 at 09:37:46AM +0000, Mathias Bur=E9n wrote: >> On 31 January 2011 08:52, Keld J=F8rn Simonsen wro= te: >> > 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 Lin= ux >> 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 dat= a > 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@vger.kernel.org > More majordomo info at =A0http://vger.kernel.org/majordomo-info.html > --=20 Roberto Spadim Spadim Technology / SPAEmpresarial -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html