# Lustre 1.8.7 server and 1.8.7 client
# dd if=/dev/zero of=/work/d/desantis.admin/lustre-1.8.7.outfile bs=500M count=4
4+0 records in
4+0 records out
2097152000 bytes (2.1 GB) copied, 9.70101 s, 216 MB/s

# dd if=/dev/zero of=/work/d/desantis.admin/lustre-1.8.7.outfile.2 bs=100M count=11
11+0 records in
11+0 records out
1153433600 bytes (1.2 GB) copied, 57.4766 s, 20.1 MB/s

# Lustre 1.8.7 server and 1.8.9 client
# dd if=/dev/zero of=/work/d/desantis.admin/lustre-1.8.9.outfile bs=500M count=4
4+0 records in
4+0 records out
2097152000 bytes (2.1 GB) copied, 45.1748 s, 46.4 MB/s

# dd if=/dev/zero of=/work/d/desantis.admin/lustre-1.8.9.outfile.2 bs=100M count=11
11+0 records in
11+0 records out
1153433600 bytes (1.2 GB) copied, 15.0094 s, 76.8 MB/s

The smaller file wins on 1.8.9, but the larger file loses without any striping set.  By default, the stripe count is set to 1.  If I set the stripe count to -1, both versions manifest good results.  Please see below.

# Lustre 1.8.7 
# lfs getstripe lustre-1.8.7.outfile 
lustre-1.8.7.outfile
lmm_stripe_count:   14
lmm_stripe_size:    1048576
lmm_stripe_offset:  3

# dd if=/dev/zero of=/work/d/desantis.admin/lustre-1.8.7.outfile bs=500M count=4
4+0 records in
4+0 records out
2097152000 bytes (2.1 GB) copied, 7.16775 s, 293 MB/s

# Lustre 1.8.9
# lfs getstripe lustre-1.8.9.outfile 
lustre-1.8.9.outfile
lmm_stripe_count:   14
lmm_stripe_size:    1048576
lmm_stripe_offset:  13

# dd if=/dev/zero of=/work/d/desantis.admin/lustre-1.8.9.outfile bs=500M count=4
4+0 records in
4+0 records out
2097152000 bytes (2.1 GB) copied, 7.77031 s, 270 MB/s

The performance is very close at this point, not enough for users to notice.