4334 Improve ZFS N-way mirror read performance

*** 547,556 ****
--- 547,562 ----
                      "both DKIOCGMEDIAINFO{,EXT} calls failed, %d\n",
                      vd->vdev_path, error);
                  pbsize = DEV_BSIZE;
          }
  
+         /*
+          * Determine the rotation
+          */
+         vd->vdev_rotation_rate = VDEV_RATE_UNKNOWN;
+         /* TODO: Implement when there's an ioctl which provides this info. */
+ 
          *ashift = highbit(MAX(pbsize, SPA_MINBLOCKSIZE)) - 1;
  
          if (vd->vdev_wholedisk == 1) {
                  int wce = 1;