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    SubjectRe: [ANNOUNCE] Ramback: faster than a speeding bullet
    On Thu 2008-03-13 12:03:03, Daniel Phillips wrote:
    > On Thursday 13 March 2008 12:50, David Newall wrote:
    > > Daniel Phillips wrote:
    > > > The period where you cannot access the data is downtime. If your script
    > > > just does a cp from a disk array to the ram device you cannot just read
    > > > from the backing store in that period because you will need to fail over
    > > > to the ramdisk at some point, and you cannot just read from the ramdisk
    > > > because it is not populated yet.
    > >
    > > Wouldn't a raid-1 set comprising disk + ramdisk do that with no downtime?
    >
    > In raid1, write completion has to wait for write completion on all
    > mirror members, so writes run at disk speed. Reads run at ramdisk
    > speed, so your proposal sounds useful, but ramback aims for high
    > write performance as well.

    raid1 + kflushd tweak?

    special raid1 mode that signals completion when it hits _one_ of the
    drives, and does sync when the slower drive is idle?
    Pavel
    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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