On Sun, Dec 20, 2009 at 10:28 AM, Roger Heflin <rogerheflin@xxxxxxxxx> wrote: > Michael Evans wrote: >> >> On Sat, Dec 19, 2009 at 1:35 PM, Roger Heflin <rogerheflin@xxxxxxxxx> >> 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@xxxxxxxxxxxxxxx >>> 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. > Wow, I had no idea these even existed (but I now know that I have to use -really- specific search terms to find them). The searches, 8-port pci-e OR pciexpress OR pci-express 16-port pci-e OR pciexpress OR pci-express yield the desired results on Google's product search, though there seems to be only one manufacturer, and only one seller currently. I guess most people building >6 drive arrays have the cash to waste on limited boxed solutions or higher-end hardware controllers that abstract the details (and often flexibility) from the system. I'll have to remember the search for the next time I buy upgrade/replacement hardware. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
