From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stan Hoeppner Subject: Re: Performance question, RAID5 Date: Sat, 29 Jan 2011 18:15:46 -0600 Message-ID: <4D44ADB2.9090707@hardwarefreak.com> References: <20110130035352.1d72e8d1@natsu> <20110130045706.4e8d6fa2@natsu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20110130045706.4e8d6fa2@natsu> Sender: linux-raid-owner@vger.kernel.org To: Roman Mamedov Cc: =?ISO-8859-1?Q?Mathias_Bur=E9n?= , Linux-RAID List-Id: linux-raid.ids Roman Mamedov put forth on 1/29/2011 5:57 PM: > On Sat, 29 Jan 2011 23:44:01 +0000 > Mathias Bur=C3=A9n wrote: >=20 >> Controller device @ pci0000:00/0000:00:16.0/0000:05:00.0 [sata_mv] >> SCSI storage controller: HighPoint Technologies, Inc. RocketRAID >> 230x 4 Port SATA-II Controller (rev 02) >> host6: [Empty] >> host7: /dev/sde ATA SAMSUNG HD204UI {SN: S2HGJ1RZ800964 } >> host8: /dev/sdf ATA WDC WD20EARS-00M {SN: WD-WCAZA1000331} >> host9: /dev/sdg ATA SAMSUNG HD204UI {SN: S2HGJ1RZ800850 } >=20 > Does this controller support PCI-E 2.0? I doubt it. > Does you Atom mainboard support PCI-E 2.0? I highly doubt it. > And if PCI-E 1.0/1.1 is used, these last 3 drives are limited to 250 = MB/sec. > in total, which in reality will be closer to 200 MB/sec. >=20 >> It's all SATA 3Gbs. OK, so from what you're saying I should see >> significantly better results on a better CPU? The HDDs should be abl= e >> to push 80MB/s (read or write), and that should yield at least 5*80 = =3D >> 400MB/s (-1 for parity) on easy (sequential?) reads. >=20 > According to the hdparm benchmark, your CPU can not read faster than = 640 > MB/sec from _RAM_, and that's just plain easy linear data from a buff= er. So it > is perhaps not promising with regard to whether you will get 400MB/se= c reading > from RAID6 (with all the corresponding overheads) or not. It's also not promising given that 4 of his 6 drives are WDC-WD20EARS, = which suck harder than a Dirt Devil at 240 volts, and the fact his 6 drives d= on't match. Sure, you say "Non matching drives are what software RAID is fo= r right?" Wrong, if you want best performance. About the only things that might give you a decent boost at this point = are some EXT4 mount options in /etc/fstab: data=3Dwriteback,barrier=3D0 The first eliminates strict write ordering. The second disables write = barriers, so the drive's caches don't get flushed by Linux, and instead work as t= he firmware intends. The first of these is safe. The second may cause so= me additional data loss if writes are in flight when the power goes out or= the kernel crashes. I'd recommend adding both to fstab, reboot and run you= r tests. Post the results here. If you have a decent UPS and auto shutdown software to down the system = when the battery gets low during an outage, keep these settings if they yield substantially better performance. --=20 Stan -- 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