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    SubjectRe: IDE hotplug support?
      Why not just grab a pair of 8 port 3ware cards?  Run raid 5 on each 
    card, and throw 0 or linear via the md driver on top?

    Jakob Østergaard wrote:

    >On Thu, May 02, 2002 at 08:19:04PM +0200, Martin Dalecki wrote:
    >...
    >
    >
    >>15 drives == 16 interfaces == 8 channels == 4 controllers
    >>with primary and secondary channel.
    >>
    >>
    >
    >Usually using both master and slave on an IDE channel spells disaster
    >performance wise, and I would be surprised if the hotplug stuff worked
    >with this as well...
    >
    >
    >
    >>He will have groups of about 4 drives on each channel wich
    >>serialize each other due to excessive IRQ line sharing and
    >>master slave issues.
    >>
    >>
    >
    >Use 8 controllers for the 15 (16) drives.
    >
    >
    >
    >>8 x 130MBy/s >>>> PCI bus throughput... I would rather recommend
    >>a classical RAID controller card for this kind of
    >>setup.
    >>
    >>
    >
    >Because RAID controllers do not use the PCI bus ??? ;)
    >
    >The bus-overhead on RAID-5 is not too bad unless you specifically construct
    >a workload to make it so (writes-only, scattered so that the kernel cannot
    >cache stripes to avoid read-in for parity calculation).
    >
    >Sure, the PCI bus will be a bottleneck, and PCI overhead alone will decrease
    >the real-world performance to somewhere below the theoretical PCI bandwidth
    >limitations, but don't let this blind you - 100 MB/sec sustained transfers
    >can still be "good enough" for many people.
    >
    >By the way, has anyone tried such larger multi-controller setups, and tested
    >the bandwidth in configurations with multiple PCI busses on the board, versus a
    >single PCI bus ?
    >
    >
    >


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