vmax 20k synchronization rate

i've been watching an adaptive copy process and the sync rate is very slow. less than 10MB/s. I reviewed the performance on the array and the heatmap is fine, the fa's are fine, the device utilization is good, etc. Link bandwidth is ok.

How does one determine why the synchronization rate is low? the paste is from the R2 side. There's not a lot of invalid tracks at this point.

Device Group (DG) Name	: rdf-npesx0236
DG's Type	: RDF2
DG's Symmetrix ID	: 000192606096	(Microcode Version: 5876)
Remote Symmetrix ID	: 000192606021	(Microcode Version: 5876)
RDF (RA) Group Number	:  19 (12)

	Target (R2) View	Source (R1) View	MODES
--------------------------------	------------------------ ----- ------------
	ST	LI	ST
Standard	A	N	A
Logical	T  R1 Inv   R2 Inv  K	T  R1 Inv   R2 Inv	RDF Pair

Device  Dev   E  Tracks   Tracks  S Dev   E  Tracks   Tracks MDAE  STATE

-------------------------------- -- ------------------------ ----- ------------

DEV001  026D WD

0

0 RW 0236 RW

0

59291 C.D.  SyncInProg

Total	-------- --------	-------- --------
Track(s)	0	0	0	59291
MB(s)	0.0	0.0	0.0   3705.7

Synchronization rate	:	5.8 MB/S
Estimated time to completion	: 00:21:53