From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roger Heflin Subject: Re: Typical RAID5 transfer speeds Date: Sun, 20 Dec 2009 12:28:43 -0600 Message-ID: <4B2E6CDB.3000707@gmail.com> References: <4B2D4731.3090702@gmail.com> <4877c76c0912192021s2c3da63au57f5dcb0391b3eb3@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4877c76c0912192021s2c3da63au57f5dcb0391b3eb3@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: Michael Evans Cc: Matt Tehonica , linux-raid@vger.kernel.org List-Id: linux-raid.ids Michael Evans wrote: > On Sat, Dec 19, 2009 at 1:35 PM, Roger Heflin wrote: >> Matt Tehonica wrote: >>> I have a 4 disk RAID5 using a 2048K chunk size and using XFS filesystem. >>> Typical file size is about 2GB-5GB. I usually get around 50MB/sec transfer >>> speed when writting files to the array. Is this typcial or is it below >>> normal? A friend has a 20 disk RAID6 using the same filesystem and chunk >>> size and gets around 150MB/sec. Any input on this?? >>> >>> Thanks, >>> Matt >> Speed depends on how the disks are connected to the system, and how many >> disks there are per connection, and what kind of disks they are. >> >> If your friend had a 20 disk raid6 on one 4port sata pci-32bit/33mhz card >> with port multipliers his total throughput would be <110mb/second reads or >> writes, if your friend had 20 disks on 10+ port pcie-x16 cards his total >> possible speed would be much much higher, reads would be expected to be >> 18x(rawdiskrate) if the machine could handle it. >> >> Also newer disks are faster than older disks. >> >> 1.5tb disks read/write at 125-130+ MB/second on a fast port. >> 1.5tb disks read/write at 75-80 MB/second on a PCI-32bit/33mhz port. >> 500gb disks read/write at 75-80 MB/second on a PCI-32bit/33mhz port. >> 250gb disks read/write at 50-55 MB/second on a fast port. >> >> And those PCI-32bit/33mhz ports are with only a single disk, put more than >> one on there, and the io rates drop...so 2 disk on pci-32bit/33mhz (old PCI) >> port will have <50MB/second each no matter how fast the disk is, put 3 on >> there and each disk is down to 33mhz, 4 25MB/second or less. >> -- >> 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 http://vger.kernel.org/majordomo-info.html >> > > Speaking of 16x 16 port cards, why is it that it's so difficult to > find an 8 or 16 port 4 or 8/16x pcie adapter? A good 1xpci-e to 2x > SATA costs like 25 to 50 USD. Given the reduction in duplicate > components, it should not be hard to make a card with 8 ports for 100 > USD or less right? I don't even want any intelligence, just normal > disk to PCI-E lane connectin would be fine. > I am pretty sure it is lack of need. I believe someone mentioned supermicro has a 8 port pcie-x4 card, that is in the $100 range, but the driver for it is kind of new and has some issues at this time.