From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen Subject: Re: Performance question, RAID5 Date: Mon, 31 Jan 2011 19:44:17 +0100 Message-ID: <20110131184417.GB27952@www2.open-std.org> 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: Content-Disposition: inline In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Roberto Spadim Cc: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen , Mathias =?iso-8859-1?Q?Bur=E9n?= , Stan Hoeppner , Roman Mamedov , CoolCold , Linux-RAID List-Id: linux-raid.ids 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 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 w= rote: > >> > 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 T= B 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 though= t > >> that it was only calculated on writes? The Atom (330) has HT, so L= inux > >> 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 w= hy > > ordinary RAID without LVM need to use so much CPU. Maybe a lot of d= ata > > sguffling between buffers? Neil? > > > > Best regards > > Keld > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-rai= d" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at =A0http://vger.kernel.org/majordomo-info.htm= l > > >=20 >=20 >=20 > --=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