[lkml]   [2005]   [Dec]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH] aic79xx should be able to ignore HostRAID enabled adapters
    On Thu, Dec 01, 2005 at 05:44:12PM +0000, Christoph Hellwig wrote:
    > On Thu, Dec 01, 2005 at 08:44:15AM -0500, Salyzyn, Mark wrote:
    > > The HostRAID driver has a specialized (ok, yes, also proprietary) CHIM
    > > and sequencer where attention can be focused on techniques of
    > > performance improvement and OS agnostics. In addition, the RAID code in
    > > that driver understands the hardware, CHIM & sequencer and takes
    > > advantage of features that just can not be performed by an abstracted dm
    > > or an LLD. RAID1 is handled under some conditions, for instance, with
    > > one DMA operation over the PCI bus rather than two duplicated for each
    > > target, greatly increasing the performance.
    > If you contributed that sequencer code and sent me a card I'm pretty sure
    > I'd love into adding support for this to a special DM module. In fact we'd
    > need somthing similar for Certain SATA boards aswell.
    > OTOH the raid flag would be useless aswell there, because we'd of course
    > support this on identical cards without the raid bios aswell :)

    I'd love to see a hardware-aware DM RAID module, since I want to do the
    same thing for sata_sx4 (Promise SX4).

    SX4 has four ATA engines, an on-card ECC-capable DIMM, and an on-card
    XOR engine. The OS driver has complete control over these facilities.
    Unfortunately, driving the card in "dumb mode" means that performance
    takes a major hit, since each transaction looks like:

    submit DMA memcpy to HDMA engine
    get HDMA interrupt
    # now, the data is on the card
    submit ATA write command
    get ATA interrupt

    All data must be copied to/from the DIMM, before the ATA engine can do
    anything. Further, there is only one HDMA engine, but 4 ATA engines.

    Ideally, RAID1 would copy the data to the card ONCE, then start 2 ATA
    engines. Ideally, RAID5 would copy the data to the card ONCE, XOR it,
    then start the ATA engines. And the rest of the DIMM should be used as
    write-through cache.

    I'm sure DM can do that, but I haven't researched how.

    I'll supply a card (and engineering help, but no docs, alas) to anyone
    interested in trying out this stuff.


    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-12-01 18:59    [W:0.031 / U:54.496 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site