I should note that I am using dm-mpath, and the i/o is fragmented on the wire when using the device mapper device node but it is not fragmented when using one of the regular /dev/sd* device nodes for that device. On Wed, Sep 16, 2009 at 8:34 AM, David Strand <dpstrand@xxxxxxxxx> wrote: > I am issuing 512 Kbyte reads through the device mapper device node to > a fibre channel disk. With 2.6.30 one read command for the entire 512 > Kbyte length is placed on the wire. With 2.6.31 this is being broken > up into 5 smaller read commands placed on the wire, decreasing > performance. > > This is especially penalizing on some disks where we have prefetch > turned off via the scsi mode page. Is there any easy way (through > configuration or sysfs) to restore the single read per i/o behavior > that I used to get? > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
