EMC VMAX – 20/40K Back-End   Connectivity Posted on December 12, 2013 by Dave Ring

Each Engine has two Directors with each Director containing two

Back-End Fibre Channel I/O Modules (Labeled MOD0 & MOD1).

These modules (also known as DA’s – Disk Adapters) provide Fibre

Channel Connectivity to the drives. As you can see from the image

below there is just a single physical port on the Back-end IO Module,

this single port is a Quad SFP port (QSFP). The connecting cable has

a single copper QSFP transceiver connector consisting of 4 Fibre

channel cables aggregated into one Single QSFP port. While at the

Drive Bay side the 4 Fibre channel cables branch out as individual

connections to the link control cards (LCC) as we will see shortly.

Each DAE contains two LCC cards (LCCA & LCCB).

The Engine diagram below provides the Port layout on the Engine and

as you can see the lower director is the odd director and the upper

director is the even director. On both directors there are two Back-

end IO modules (MOD0 & MOD1) per director, the Back End IO

Module MOD0 has connections A0,A1,B0,B1 and MOD1 has

connections C0,C1,D0,D1.

Here is an example of a Standard VMAX Storage Bay Configuration

fully populated (8 Engines) with 10 storage BAYS as if viewed from

the Front of the VMAX. In this fully populated configuration you have

four direct connect storage bays (Bay 1’s) and six daisy chained

Storage Bays (2’s & 3’s). Each octant represents connectivity from a

Single Engine (2 x Directors).

In order to keep this example simple I will focus on the First Engine in

the VMAX which is Engine 4. Understanding how one engine connects

to the backend will help to understand the remaining Back-end

connectivity as the same rules apply. Below is ‘Disk Bay 1A’ with

DAE’s 1-8 populated, these are the DAE’s that Engine4 directly

connects to:

Engine 4 Backend IO Modules and QSFP Cables: Here are the four

slics (MOD’s) on the Engine with each slic providing 4x4Gig FC links

(Loops)

We can see from the labeling on the image below of Engine4 that the

Even Director (DIR8) connects to LCCB and the Odd Director

(DIR7) connects to LCCA. MOD0 on both the even and odd directors

connect to DAE’s 1,5,2,6 with MOD1 on both directors connecting to

DAE’s 3,7,4,8.

http://davering.files.wordpress.com/2013/12/vmax_be6.jpg

Checking the connectivity on DAE 1 you can see MOD0 from the Even

Director (Dir8) connects to the primary port on LCCB and MOD0 from

the Odd Director (Dir7) connects to the primary port on LCCA. Note

that all connections from the Even Directors connect to LCCB and all

the Odd directors connect to the LCCA cards. On the loop

configuration you can see that DAE1 is on Loop0. There are 8

Redundant Loops in total from the Engine:

DAE1=LOOP0 (A0(P1))

DAE2=LOOP2 (B0(P3))

DAE3=LOOP4 (C0(P1))

DAE4=LOOP6 (D0(P3))

DAE5=LOOP1 (A1(P2))

DAE6=LOOP3 (B1(P4))

DAE7=LOOP5 (C1(P2))

DAE8=LOOP7 (D1(P4))

http://davering.files.wordpress.com/2013/12/vmax_be8.jpg

Here is the full connectivity map for Engine 4: Also note the following

translations for MOD0 A0=P1 A1=P2 B0=P3 B1=P4 and likewise for

MOD1 C0=P1 C1=P2 D0=P3 D1=P4

This completes the example of the direct attach Back-end cabling for

Engine 4. The same rules apply as you add more engines. As a result

of this design the back-end cabling provides dual access across

directors to each drive eliminating any single point of failure (8

Redundant Loops).

To Summarize:

• 8 Redundant Loops – A0,A1,B0,B1,C0,C1,D0,D1

• LCCA Connects to the ODD number Director

• LCCB Connects to the EVEN number Director

• Each Engines supports a seperate octant

• Each Slic (MOD) has 4x4Gig FC Links

Note: Please reference EMC Documentation for more detailed

information specific to your configuration. Depending on Engine

counts and Direct/Daisy configurations your cabling may expand

differently.