[lkml]   [2007]   [Feb]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: SATA-performance: Linux vs. FreeBSD
    > > 
    > The problem is: FreeBSD is fast, but lacks of some special drivers. Linux has
    > all drivers but access to harddisk is unpredictable and thus unreliable!
    > What can I do??

    there's several tunables you can do;
    1) increase /sys/block/<device>/queue/nr_requests
    the linux default is on the low side
    2) investigate other elevators; cfq is great for interactive use but not
    so great for max throughput. you can do this by echo'ing "deadline"
    into /sys/block/<device>/scheduler
    3) make sure ext3 is set to "data=writeback"; the default journalling
    mode is very strict, fine for smallish files but for multi-gigabyte
    it'll start to hurt
    4) try to use iostat -x /dev/<foo> 1 to see what values avg-rq and
    avg-qu are.. avg-rq should be at least several hundred if not more.
    5) echo a larger value into /sys/block/<device>/queue/max_sectors_kb
    the default seems to be 512 which is... really low. The hw max is in
    another file in that directory; if you want max throughput set the
    max_sectors_kb value to the hw max. (you pay in terms of fairness for
    this; it's the eternal fairness/latency versus throughput tradeoff)

    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: 2007-02-13 11:11    [W:0.042 / U:2.104 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site