On Wed, Sep 02, 2009 at 05:51:35PM +0300, Alexander Motin wrote: > To completely load gmirror on read operations, you may need to run > two dd's same time. Also make sure, that your gmirror runs in > round-robin mode. Default split mode, which should help with linear > read, is IMHO ineffective, at least with default MAXPHYS and slice > values. On that note, there is an excellent patch in this PR which improves the way gmirror schedules read requests to different disks: http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/113885 Could someone please commit this? With this patch and a two-way mirror, I can run two linear scans of different files in parallel and get almost perfect scaling. (result: this approximately halves the wall-clock time it takes to do a backup of some fat VM images) IIRC, without the patch it's faster to run them sequentially. :( --EmilReceived on Wed Sep 02 2009 - 22:21:10 UTC
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