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: Sun, 30 Jan 2011 06:56:16 +0100 Message-ID: <20110130055616.GA13022@www2.open-std.org> References: <20110130035352.1d72e8d1@natsu> <20110130015231.GA1435@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: Mathias =?iso-8859-1?Q?Bur=E9n?= Cc: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen , Linux-RAID List-Id: linux-raid.ids On Sun, Jan 30, 2011 at 01:54:42AM +0000, Mathias Bur=E9n wrote: > On 30 January 2011 01:52, Keld J=F8rn Simonsen wrot= e: > > On Sat, Jan 29, 2011 at 11:44:01PM +0000, Mathias Bur=E9n wrote: > >> On 29 January 2011 22:53, Roman Mamedov wrote: > >> > On Sat, 29 Jan 2011 22:48:06 +0000 > >> > Mathias Bur=E9n wrote: > >> > > >> >> Hi, > >> >> > >> >> I'm wondering if the performance I'm getting is OK or if there'= s > >> >> something I can do about it. Also, where the potential bottlene= cks > >> >> are. > >> > > >> > How are your disks plugged in? Which controller model(s), which = bus. > >> > But generally, on an Atom 1.6 Ghz those seem like good results. > >> > > >> > -- > >> > With respect, > >> > Roman > >> > > >> > >> > >> Hi, > >> > >> Sorry, of course I should've included that. Here's the info: > >> > >> ~/bin $ sudo ./drivescan.sh > >> Controller device @ pci0000:00/0000:00:0b.0 [ahci] > >> =A0 SATA controller: nVidia Corporation MCP79 AHCI Controller (rev= b1) > >> =A0 =A0 host0: /dev/sda ATA Corsair CSSD-F60 {SN: 1032650558000999= 0027} > >> =A0 =A0 host1: /dev/sdb ATA WDC WD20EARS-00M {SN: WD-WCAZA1022443} > >> =A0 =A0 host2: /dev/sdc ATA WDC WD20EARS-00M {SN: WD-WMAZ20152590} > >> =A0 =A0 host3: /dev/sdd ATA WDC WD20EARS-00M {SN: WD-WMAZ20188479} > >> =A0 =A0 host4: [Empty] > >> =A0 =A0 host5: [Empty] > > > > > > Hmm, it seems like you have 2 empty slots on the on-board =A0SATA > > controller. Try to move 2 of the disks from the other controller to= the > > on-board controller. > > > > And I would also avoid LVM. I think LVM affects striping. > > > > best regards > > Keld > > >=20 > Sadly the 2 empty slots are not to be found on the motherboard, I > guess they're in the chipset only. maybe then use the 5th drive on the sata on-board controller in the raid5 - the sda drive. If the raid5 is where you want performance from.= =20 what do you use sda for? Your OS? It is a lot of space to use just for the OS. It could easily go into the raid5 too. And you culd use a raid for the system too, to secure you from bad things happening to your system. Or you could have a few 5 to 10 GB partitions in the beginning of each drive, for experimenting with raid layout and performance.=20 This should be outside any LVM to exclude LVM having an impact on=20 the tests.=20 Maybe your PCI-e cannot do more than 2.5 Gbit - then 2 of your disks would be enough to fill that connection. You could try out a raid0 on the 3 drives. If you cannot get more than about 300 MB/s, th= en=20 the PCI-E is a bottleneck.=20 If that is so, then having 3 drives from the PCI-E could slow down the whole raid5, and using only 2 drives could speed up the full raid5. The on-board sata controller is normally much faster, having a direct connection to the southbridge - and typically a speed in the neighbourh= ood of 20 Gbit - or 2500 MB/s - which would be enough for many systems to not be the bottleneck. It can often pay off to have a motherboard with two on-board sata controllers with in total 8 SATA ports or more, instead of bying an extra PCI-E controller. Looking forward to hear what you find out. best regards keld -- 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