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. -- 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
