lkml.org 
[lkml]   [2006]   [Jan]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: io performance...
    Date
    Max Waterman <davidmaxwaterman+kernel@fastmail.co.uk> writes:

    > Phillip Susi wrote:
    >> Right, the kernel does not know how many disks are in the array, so
    >> it can't automatically increase the readahead. I'd say increasing
    >> the readahead manually should solve your throughput issues.
    >
    > Any guesses for a good number?
    >
    > We're in RAID10 (2+2) at the moment on 2.6.8-smp. These are the block
    > numbers I'm getting using bonnie++ :
    >
    >[...]
    > We're still wondering why rd performance is so low - seems to be the
    > same as a single drive. RAID10 should be the same performance as RAID0
    > over two drives, shouldn't it?

    I think bonnie++ measures accesses to many small files (INN-like
    simulation) and database accesses. These are random accesses, which
    is the worst access pattern for RAID. Seek time in a RAID equals the
    longest of all the drives in the RAID, rather than the average. So
    bonnie++ is domninated by your seek time.

    Ian


    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2006-01-20 14:45    [W:6.367 / U:0.064 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site