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    SubjectRe: Increase dirty_ratio and dirty_background_ratio?
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    On Fri, 2009-01-09 at 14:31 -0800, david@lang.hm wrote:

    > for that matter, it's not getting to where it makes sense to have wildly
    > different storage on a machine
    >
    > 10's of GB of SSD for super-fast read-mostly
    > 100's of GB of high-speed SCSI for fast writes
    > TB's of SATA for high capacity
    >
    > does it make sense to consider tracking the dirty pages per-destination so
    > that in addition to only having one process writing to the drive at a time
    > you can also allow for different amounts of data to be queued per device?
    >
    > on a machine with 10's of GB of ram it becomes possible to hit the point
    > where at one point you could have the entire SSD worth of data queued up
    > to write, and at another point have the same total amount of data queued
    > for the SATA storage and it's a fraction of a percent of the size of the
    > storage.

    That's exactly what we do today. Dirty pages are tracked per backing
    device and the writeback cache size is proportionally divided based on
    recent write speed ratios of the devices.


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